Mar 142013
 

I often see people using zone starts and/or quality of competition as a way to justify any players unexpectedly poor or unexpectedly good play. Player X has a bad goal or corsi ratio because he plays all the tough minutes (i.e. the defensive zone starts and against the oppositions best lines). I am pretty certain that quality of competition is vastly over emphasized (everyone plays against everyone to some extent) and is vastly overshadowed by individual skill and quality of teammates, and I think zone starts do as well.

Eric Tulsky at NHL Numbers.com posted a good review of the research into the zone start effects on corsi statistics and I recommend people give that a read. I want to look into the issue a little further though. Most of the attempts to identify the impact of zone starts on a players stats have been inferred by looking at the league-wide correlations or by actual counting of how many shots are taken after a zone face off. Both of these have their faults. As Eric Tulsky pointed out, taking a correlation of every players corsi with their zone start stats doesn’t take into account that it is the top line players that usually get the offensive zone starts and thus this likely over estimates the impact as these players do take more shots regardless of their zone start. Eric Tulsky also took the time to count the number of fenwick events that occur between an offensive zone face off and the time the puck leaves the offensive zone and estimated that to be 0.31. This would imply that every extra offensive zone start a player takes is worth 0.31 fenwick events. Of course, this doesn’t take into account that the best offensive players in the league typical get more  offensive zone starts but it also doesn’t consider what happens after the puck leaves the zone. If the puck leaves the zone under the opposing teams control there is probably a negative fenwick effect for the next several seconds of play reducing the 0.31 number further.

I want to get beyond these issues by taking a look at how zone starts affect individual players. I have previously argued that after 10 seconds of an offensive/defensive zone face off the majority of the benefit (or penalty) of an offensive (or defensive zone) face off has worn off. I wanted to take it a bit further to be sure that there is no residual effect and chose to conduct this analysis using a 45 second cut off. So, any time within 45 seconds of an offensive or defensive zone face off with no other stoppages in play will be eliminated in my face off adjusted data. This should eliminate pretty much every second of every shift that started with an offensive or defensive zone face off leaving just the play that occurred after a neutral zone face off or on the fly changes. I am going to call this ice time F45 ice time and it will represent ice time that is not in any way affected by zone starts. With this in mind, I will take a look at the differences between straight 5v5 stats and the F45 stats and the differences will give me an indication of how significant zone starts impact a players stats.

To do this I will look at both corsi for and corsi against stats on a per 20 minutes of ice time basis. It should be noted that corsi rates are about 7.5% higher during the f45 play (goal rates are ~15% higher!) so I will reduce the f45 corsi rates by 7.5% to account for this and conduct a fair comparison (previous zone start studies may have been impacted by this as well). Now, let’s take a look at eight players (Manny Malhotra, Dave Bolland, Brian Boyle, Jay McClement, Tanner Glass, Brandon Sutter, Adam Hall, and Taylor Pyatt) with an excess of defensive zone starts.

OZ% DZ% OZ%-DZ% FF20 FA20 FF%
Malhotra 12.2 54.6 -42.4 -3.09% 1.09% -1.0%
Bolland 19.8 40.5 -20.7 8.94% -5.25% 3.5%
B. Boyle 21.0 40.2 -19.2 2.87% 8.74% 0.3%
McClement 24.8 41.9 -17.1 -0.31% 1.34% -0.4%
Glass 20.5 37.1 -16.6 4.39% -6.00% 2.6%
Sutter 23.1 36.6 -13.5 -2.67% 2.32% -1.2%
Hall 20.7 33.9 -13.2 -4.06% 4.59% -2.2%
Pyatt 24.0 36.4 -12.4 0.38% -0.25% 0.2%
Average 20.8 40.2 -19.4 0.81% 0.82% 0.23%

The FF20 and FA20 columns show the % change in from 5v5 play to F45 play and the FF% column shows the 5v5 FF% – F45 FF%. The averages are a straight average, not weighted for ice time or zone starts. For players that have a significant defensive zone bias we would expect their F45 play to exhibit an increase in FF20 and a decrease in FA20 resulting in an increase in FF%. In bold are the circumstances where this in fact did happen. As you can see, this isn’t the majority of the time. It is actually kind of surprising that these heavily defensive zone start biased players didn’t see a significant and systematic improvement in their fenwick rates.

Now, let’s take a look at eight players (Henrik Sedin, Patrick Kane, Maian Gaborik, Justin Abdelkader, Kyle Wellwood, Tomas Vanek, John Tavares, Jason Arnott) who had a heavy offensive zone start bias.

OZ% DZ% OZ%-DZ% FF20 FA20 FF%
H. Sedin 49.3 16.2 33.1 -3.72% 1.81% -1.4%
P. Kane 41.4 20.3 21.1 5.94% 4.66% 0.3%
Gaborik 39.0 22.8 16.2 0.60% 2.32% -0.4%
Abdelkader 37.5 26.0 11.5 3.93% 3.49% 0.1%
K. Wellwood 36.9 27.6 9.3 4.54% -2.32% 1.7%
Vanek 36.2 27.2 9.0 -3.39% 1.06% -1.1%
Tavares 35.8 27.2 8.6 -2.39% 1.83% -1.0%
Arnott 36.4 28.0 8.4 -3.41% 1.81% -1.3%
Average 39.1 24.4 14.7 0.26% 1.83% -0.39%

For offensive zone start biased players we would expect to see their FF20 decrease, FA20 increase and FF% decrease when we remove their zone start bias. This is mostly true for FA10 (only Wellwood deviated from expectations) but less true for FF20 and FF% and overall the adjustments were relatively minor. Henrik Sedin had the greatest negative impact to his FF% but it only took him from a 55.2% fenwick player to a 53.8% fenwick player which is still pretty good. This could very well be an upper bound on the benefit of excessive offensive zone starts.

Eric Tulsky also presented a paper at the recent Sloan Sports Analytics Conference in which he suggested that a successful zone entry via carrying the puck in is worth upwards of 0.60 fenwick and upwards of 0.28 fenwick on a dump in. As pointed out earlier, Eric Tulsky counted o.31 fenwick between an offensive zone face off and the puck clearing the zone so and if the other team is clearing the zone with control of the puck, it is certainly possible that they will generate almost as many shots on their subsequent counter-rush essentially negating much of the benefit of the offensive zone start. Without studying zone exits and how frequently zone exists result in successful zone entries into opposing teams end we won’t know for sure, but the data shown above indicates that this might be the case.

The next question that might be worth exploring is, if there is no significant benefit to starting your offensive players in the offensive zone, is there a penalty? For example, might it be better for the Canucks to start the Sedin’s solely in the defensive and neutral zones on the theory that their talent with the puck will allow them to more frequently carry the puck into the offensive zone which, as Eric Tulsky showed, more frequently results in shots and goals. I am not certain of that but might be worthy of further investigation.  I suspect again any benefit/penalty of any zone start deployment will largely be overshadowed by the players individual ability and the quality of their line mates. The ability to win puck battles, control the puck and move it up the ice is the real driver of stats, not usage of the player.

All of this is to say that coaching strategy (at least player usage strategy) is probably not a significant factor in the statistical performance of the players or the outcomes of games and I suspect, as I previously found, the majority of the benefit of an offensive zone start is those situations where you win a face off, take a shot resulting in a goal or the goalie catching it or covering it for another face off.  If the play goes beyond that individual talent (puck retrieval for example) takes over and the opposition will get an opportunity to counter attack. This is why, as I previously determined, eliminating the first 10 seconds after a face off is sufficient for eliminating the majority of the effects of a zone start and even then, the effects are probably not as significant as we think they should be.

 

Mar 112013
 

There has been a fair bit of talk recently about Tyler Bozak and what the Leafs should do with him as he is clearly not suited for his #1C role but is set to be a UFA this summer and if the Leafs intend to keep him he’ll need a new contract.  To get an idea of his worth, I decided to see if I could identify a few comparable players.

Let’s start off offensively. The first thing I looked at was primary points per 60 minutes of 5v5 ice time (primary points = goals + first assists). From last year through this past weekend’s games Bozak had a PrPts/60of 1.085 so as an initial cut off I pared down the list of comparable players to forwards a PrPts/60 of between 1.00 and 1.20 and who have had at least 1000 minutes of ice time. There are some pretty good players in this list such as Ryan Getzlaf, Stephen Weiss, Tomas Plekanec and Daniel Breiere but there are some less talented players like Eric Nystrom and Marcel Goc.

The next thing I considered is Primary Points Percentage (PrPts%), or the percentage of goals scored while the player was on the ice. Tyler Bozak’s PrPts% is a relatively weak 41.24% (Getzlaf, for example, is 52.38% and Plekanec’s is 56.22%). I then pared down the list to just include centers and this is what I came up with as comparable offensive centers, sorted by PrPts%.

Player Team PPts/60 PrPts%
NIELSEN, FRANS NY Islanders 1.091 47.98%
SMITH, ZACK Ottawa 1.008 46.67%
VERMETTE, ANTOINE Phoenix 1.173 46.55%
LETESTU, MARK Columbus 1.138 46.32%
NUGENT-HOPKINS, RYAN Edmonton 1.182 46.14%
ZUBRUS, DAINIUS New Jersey 1.12 45.31%
KRUGER, MARCUS Chicago 1.115 43.78%
HANZAL, MARTIN Phoenix 1.078 42.27%
STAJAN, MATT Calgary 1.064 41.87%
BOZAK, TYLER Toronto 1.085 41.24%
KOIVU, SAKU Anaheim 1.15 38.49%

That is a list of mostly 2nd and 3rd line centers along with not yet fully developed Nugent-Hopkins. So, what about Bozak defensively? To evaluate defensive play I looked at the players 5v5 corsi events against per 20 minutes (CA20) and the ratio of the players CA20 vs his team mates CA20 when they are not playing with him (TMCA20). This gives us an indication of whether their team mates are improving their defensive stats while on the the ice with the player.

Player Name Team CA20 CA20/TMCA20
ZUBRUS, DAINIUS New Jersey 14.309 0.77
LETESTU, MARK Columbus 17.034 0.90
STAJAN, MATT Calgary 17.312 0.91
HANZAL, MARTIN Phoenix 18.122 0.93
VERMETTE, ANTOINE Phoenix 17.762 0.97
NIELSEN, FRANS NY Islanders 18.307 1.01
KOIVU, SAKU Anaheim 17.114 1.02
SMITH, ZACK Ottawa 18.771 1.04
KRUGER, MARCUS Chicago 15.940 1.05
BOZAK, TYLER Toronto 21.155 1.08

For CA20/TMCA20, the lower the number the better as this indicates their line mates CA20 is better with the player than not with the player. Bozak ranks dead last in this category and also ranks dead last (by a significant margin) in CA20.

So, what does this tell us about Tyler Bozak?  Well, it probably means he has 3rd line offensive ability but it is very questionable whether he is good enough defensively be a useful 3rd liner. As for the best comparable to Tyler Bozak, I’d have to say either Marcus Kruger or Matt Stajan or maybe Frans Nielsen but Bozak is probably somewhat below all of them in terms of value due to his poor defensive play.

 

Mar 062013
 

One of the surprise player performances so far this season is that of Jakub Voracek. Voracek currently sits tied for 7th in points with 10 goals and 27 points in 24 games.  That puts him on pace to score 54 points in this lock-out shortened 48 game season which is 4 points more than he has scored in any 82 game season (career best was  50 points in 2009-10 in 81 games).

Last season when Rick Nash was on the trade block I wrote an article about Nash and in it I had a few comments about Jakub Voracek as part of a WOWY analysis. Here is what I wrote:

Nash played best when he was paired up with Voracek and Brassard and only Voracek, Brassard and Huselius made Nash a better offensive player when playing with him.  Vermette, Umberger and Malhotra were drags on his offensive numbers.  When playing apart, Voracek’s numbers are better than Nash’s.  Same for Brassard’s (who is doing it again this year, 0.782 GF20 vs Nash’s 0.613 when apart).  As an aside, the numbers suggest that Voracek is a very good offensive player  and it was probably a big mistake to trade him.  It also suggest that the Flyers aren’t getting full value from him by playing him primarily with Maxime Talbot.  If someone acquired Voracek and put him in the right situations, he could be the next Joffrey Lupul.

Voracek wasn’t traded but the departure of James van Riemsdyk and Jaromir Jagr opened up some spots on the top two lines and Voracek got a promotion from playing mostly with Talbot to playing with Claude Giroux and getting lots of powerplay time.  The results of that move are, as I predicted, very Joffrey Lupul like. Lupul put up solid but unspectacular numbers while mostly been given second line minutes and secondary power play minutes for the majority of his career. Lupul’s numbers looked unspectacular but were actually quite good considering his usage as a secondary offensive player and the quality of line mates he played with. When Lupul came to Toronto and was put on a line with another elite offensive player, given first line minutes, and first power play unit minutes, he started putting up high end offensive numbers. It wasn’t so much that Lupul had a break out season or that he had a career year, its more than he was finally given an opportunity to play with top end talent and given first line minutes.  The exact same thing happened with Voracek.  He put up solid numbers while given secondary minutes in secondary offensive roles and just needed to be given a chance to prove his worth as a first line player with quality line mates. Now he has been given that chance and the results are clear. He is a high end offensive talent.

 

Feb 272013
 

The last several days I have been playing around a fair bit with team data and analyzing various metrics for their usefulness in predicting future outcomes and I have come across some interesting observations. Specifically, with more years of data, fenwick becomes significantly less important/valuable while goals and the percentages become more important/valuable. Let me explain.

Let’s first look at the year over year correlations in the various stats themselves.

Y1 vs Y2 Y12 vs Y34 Y123 vs Y45
FF% 0.3334 0.2447 0.1937
FF60 0.2414 0.1635 0.0976
FA60 0.3714 0.2743 0.3224
GF% 0.1891 0.2494 0.3514
GF60 0.0409 0.1468 0.1854
GA60 0.1953 0.3669 0.4476
Sh% 0.0002 0.0117 0.0047
Sv% 0.1278 0.2954 0.3350
PDO 0.0551 0.0564 0.1127
RegPts 0.2664 0.3890 0.3744

The above table shows the r^2 between past events and future events.  The Y1 vs Y2 column is the r^2 between subsequent years (i.e. 0708 vs 0809, 0809 vs 0910, 0910 vs 1011, 1011 vs 1112).  The Y12 vs Y23 is a 2 year vs 2 year r^2 (i.e. 07-09 vs 09-11 and 08-10 vs 10-12) and the Y123 vs Y45 is the 3 year vs 2 year comparison (i.e. 07-10 vs 10-12). RegPts is points earned during regulation play (using win-loss-tie point system).

As you can see, with increased sample size, the fenwick stats abilitity to predict future fenwick stats diminishes, particularly for fenwick for and fenwick %. All the other stats generally get better with increased sample size, except for shooting percentage which has no predictive power of future shooting percentage.

The increased predictive nature of the goal and percentage stats with increased sample size makes perfect sense as the increased sample size will decrease the random variability of these stats but I have no definitive explanation as to why the fenwick stats can’t maintain their predictive ability with increased sample sizes.

Let’s take a look at how well each statistic correlates with regulation points using various sample sizes.

1 year 2 year 3 year 4 year 5 year
FF% 0.3030 0.4360 0.5383 0.5541 0.5461
GF% 0.7022 0.7919 0.8354 0.8525 0.8685
Sh% 0.0672 0.0662 0.0477 0.0435 0.0529
Sv% 0.2179 0.2482 0.2515 0.2958 0.3221
PDO 0.2956 0.2913 0.2948 0.3393 0.3937
GF60 0.2505 0.3411 0.3404 0.3302 0.3226
GA60 0.4575 0.5831 0.6418 0.6721 0.6794
FF60 0.1954 0.3058 0.3655 0.4026 0.3951
FA60 0.1788 0.2638 0.3531 0.3480 0.3357

Again, the values are r^2 with regulation points.  Nothing too surprising there except maybe that team shooting percentage is so poorly correlated with winning because at the individual level it is clear that shooting percentages are highly correlated with goal scoring. It seems apparent from the table above that team save percentage is a significant factor in winning (or as my fellow Leaf fans can attest to, lack of save percentage is a significant factor in losing).

The final table I want to look at is how well a few of the stats are at predicting future regulation time point totals.

Y1 vs Y2 Y12 vs Y34 Y123 vs Y45
FF% 0.2500 0.2257 0.1622
GF% 0.2214 0.3187 0.3429
PDO 0.0256 0.0534 0.1212
RegPts 0.2664 0.3890 0.3744

The values are r^2 with future regulation point totals. Regardless of time frame used, past regulation time point totals are the best predictor of future regulation time point totals. Single season FF% is slightly better at predicting following season regulation point totals but with 2 or more years of data GF% becomes a significantly better predictor as the predictive ability of GF% improves and FF% declines. This makes sense as we earlier observed that increasing sample size improves GF% predictability of future GF% while FF% gets worse and that GF% is more highly correlated with regulation point totals than FF%.

One thing that is clear from the above tables is that defense has been far more important to winning than offense. Regardless of whether we look at GF60, FF60, or Sh% their level of importance trails their defensive counterpart (GA60, FA60 and Sv%), usually significantly. The defensive stats more highly correlate with winning and are more consistent from year to year. Defense and goaltending wins in the NHL.

What is interesting though is that this largely differs from what we see at the individual level. At the individual level there is much more variation in the offensive stats indicating individual players have more control over the offensive side of the game. This might suggest that team philosophies drive the defensive side of the game (i.e. how defensive minded the team is, the playing style, etc.) but the offensive side of the game is dominated more by the offensive skill level of the individual players. At the very least it is something worth of further investigation.

The last takeaway from this analysis is the declining predictive value of fenwick/corsi with increased sample size. I am not quite sure what to make of this. If anyone has any theories I’d be interested in hearing them. One theory I have is that fenwick rates are not a part of the average GMs player personal decisions and thus over time as players come and go any fenwick rates will begin to vary. If this is the case, then this may represent an area of value that a GM could exploit.

 

Feb 182013
 

I have some new and exciting enhancements to stats.hockeyanalysis.com for you all today. Charts, Charts, and more Charts.

Before we get to the charts though, let me also mention that I have made some modifications to my HARO, HARD and HART ratings. Most of the change is to the scale and presentation and not so much to the actual formula (though there were some tweaks there too). Instead of 1.00 being an average hockey player, 0 is and the scale has been multiplied by 100 to represent % as opposed to a ratio. So now one should interpret [Shot,Fenwick,Corsi]HARO offensive ratings to mean that when the player was on the ice his team had x% (where x is his rating) more goals [shots, fenwick, corsi] for than expected (as determined by his quality of team mates and quality of competition). This means that a positive value means more goals were scored than expected and a negative value means less goals were expected. A positive value indicates the player boosted his teams offensive performance while a negative value means he was a drag to his teams offense.

For defensive [Shot,Fenwick,Corsi]HARD ratings the effect is opposite. One should interpret the HARD ratings to mean that when the player is on the ice his team gave up x% (where his rating is x) fewer goals [shots, fenwick, corsi] than expected (as determined by quality of teammates and opposition).  So, a 10 HARO rating indicates the player boosted his teams expected goal scoring rate by 10% and a 10 HARD rating indicates the player reduced his teams expected goals against rate by 10%.  The [Shot,Fenwick,Corsi]HART ratings are simply the average of the HARO and HARD ratings.

Now on to the more exciting news, the charts. We all love charts so I have added a bunch for you all to enjoy. When you go to a player page now (i.e. Zdeno Chara) you will find a link named Visualize performance over time. Clicking this link will give you a visual representation of the players performance over the past several seasons starting in 2007-08 if their careers were active then. For example, here is Zdeno Chara’s performance charts. For forwards and defensemen there are 5 charts.

  1. Point production (G/60, A/60, First A/60 and Points/60)
  2. Individual shot, fenwick and corsi rates (shot/60, ifenwick/60, icorsi/60)
  3. HARO, HARD, FenHARO and FenHARD ratings
  4. GoalsFor%, ShotsFor%, FenwickFor% and CorsiFor%
  5. Zone Start %

This should give you a quick visualization of each players performance and how it has changed over time.

For goalies (i.e. Roberto Luongo) the only chart I have right now are 5v5 Zone Start Adjusted Save percentages.

Maybe the charts that will generate the most interest though are the new WOWY charts (sure to make you scream “WOWY!!!”). To access the WOWY charts you simply need to go to a WOWY data page and click on the “Visualize This Table” link at the top of the WOWY table (only for ‘with you’ WOWY, not ‘against you’). This will give you two WOWY bubble charts.  The first one plots teammate ‘with you’ GF% across the horizontal axis and teammate ‘without you’ GF% across the vertical access. The second chart is the same but plots CF% instead. The size of the bubbles are relative to the total TOI With.

In these plots good players will have the majority of their teammates bubbles show up below or to the right of the diagonal line from the bottom left corner to the top right corner and bad players will have the majority of their teammates above or to the left of that line. Players with a lot of teammates in the bottom right quadrant are really good because they are taking sub par players and making them look good. Players with a lot of teammates in the upper left quadrant are  bad because they make good players look bad.

For a look at two polar opposite players, take a look at Zdeno Chara’s WOWY charts compared to Jack Johnson’s WOWY charts (I have linked to the 3 year 5v5 ZS adjusted WOWY charts). Also, on Saturday I wrote a post about how bad Tyler Bozak is and if you want more evidence of that have a look at his 2 year WOWY charts. I am slowly becoming a big believer that WOWY’s are where it is at in evaluating players (though I guess I have always been a believer as this is the core of my HARO, HARD, and HART ratings). The great players are the ones who consistently make their team mates better. The good players are the ones who can really capitalize playing with great players and don’t hold them back. The bad players are those who act as drags on their team mates. These WOWY charts are a quick and easy way of visualizing the different types of players. For the Leafs, Grabovski fits into the ‘great’ category, Kessel into the ‘good’ category and Bozak into the bad.

I have a few more ideas of some charts and tables to add (I’d got some ideas for some more ‘usage’ type charts) but I think this will be the last major update for a while. That said, if you have any ideas of what you would like to see added definitely let me know and I’ll see what I can do. As for updating of the 2012-13 stats, it should be noted that they aren’t updated daily.  I have been trying (fairly successfully so far) to update them every Monday, Wednesday and Friday mornings and I hope to continue that but no guarantees.

Update: I know I said I wouldn’t do any more updates but I have made the WOWY charts better by adding WOWY charts for GF20, GA20, CF20 and CA20. Now we can easily see where a players strengths and weaknesses are (i.e. offense vs defense).

 

Feb 012013
 

Last week I introduced player TOI usage charts and one use I thought they had was to look at how a players usage changed during the downside of their careers. Today I will do just that by looking at Nicklas Lidstrom’s TOI charts over the last 5 seasons. Consider this an extension to my earlier article where I took a look at Lidstrom’s last few seasons of his career. Let’s get right at it with his 5v5 chart.

LidstromTOIChart

 

Lidstrom’s last big season was clearly 2007-08 and every year since he has been below his 2007-08 levels in terms of 5v5 ice time. What is interesting to note is how little (relatively) ice time he had during the 2010-11 season, the year he won the Norris Trophy. I think it was a big mistake that he was awarded the trophy that season and this is just a little more evidence of that. In fact, Lidstrom was 4th on the Red Wings in ESTOI/Game by defensemen which is why his TOI% in the chart above were so low that year. Rafalski retired in the summer of 2011 which meant Lidstrom would get a boost to his ice time in 2011-12.

So, what about his special teams play?

LidstromPPPKTOIChart

On the powerplay, Lidstrom maintained his level of playing ~60% of his teams 5v4 power play minutes but his penalty kill ice time dropped significantly over the final 2 seasons of his career.

Based on the above charts, the last year I think you could consider Lidstrom a true heavy work load stud of a defenseman was in 2007-08. He was still awfully good for a couple more years and quite good until he retired but his slow decline in ice time had begun.

 

Jan 302013
 

For those familiar with my history, I have been a big proponent that there is more to the game of hockey than corsi and that players can certainly drive on-ice shooting percentage. I have not done much work at the team level, but now that I have team stats up at stats.hockeyanalysis.com I figured I’d take a look.

Since shooting percentages can vary significantly over small sample sizes, my goal was to use the largest sample size possible.  As such, I used 5 years of team data (2007-08 through 2011-12) and looked at each teams shooting and save percentages over that time. During those 5 years Vancouver led all teams in 5v5 ZS adjusted save percentage shooting at 10.69% while Columbus trailed all teams with a 8.61% shooting percentage. What’s interesting to note is the top 6 teams are Vancouver, Washington, Chicago, Philadelphia, Boston and Pittsburgh, all what we would consider the teams with the best offensive talent in the league. Meanwhile, the bottom 5 teams are Columbus, Los Angeles, Phoenix, Carolina, and Minnesota, all teams (except maybe Carolina) more associated with defensive play and a defense-first system.

As far as save percentage goes, Phoenix led the league with a 91.83% save percentage while the NY Islanders trailed with an 89.04% save percentage. The top 5 teams were Phoenix, Boston, Anaheim, Nashville, and Montreal.  The bottom 5 teams were NY Islanders, Tampa, Toronto, Chicago and Ottawa. Not surprises there.

As far as sample size goes, teams on average had 7,627 shots for (or against) over the course of the 5 years which gives us a reasonable large sample size to work with.

Now, in order to not use an extreme situation, I decided to compare the 5th best team to the 5th worst team in each category and then determine the probability that their deviations from each other are solely due to randomness.  This meant I was comparing Boston to Minnesota for shooting percentage and Montreal to Ottawa for save percentage.

TeamShootingPercentageComp

As you can see, there isn’t a lot of overlap, meaning there isn’t a large probability that luck is the reason for the difference between these two teams 5 year save percentages.  In fact, the intersecting area under the two curves amounts to just a 6.2% chance that the differences are luck driven.  That’s pretty small and the differences between the teams above Boston and below Minnesota would be greater. I think we can be fairly certain that there are statistically significant differences between teams 5 year shooting percentages and considering how much player movement and coaching changes there are over the span of 5 years it makes it that much more impressive. Single seasons differences could in theory (and probably likely are) more significant.

TeamSavePercentageComp

The save percentage chart provides even stronger evidence that there are non-luck factors at play.  The intersecting area under the curves equates to a 2.15% chance that the differences are due to luck alone. There is easily a statistically significant differences between Ottawa and Montreal’s 5 year save percentages. Long-term team save percentages are not luck driven!

So, the next question is, how much does it matter?  Well, the average team takes approximately 1500 5v5 ZS adjusted shots each season. The differences in shooting percentage between the 5th best team and the 5th worst team is 1.27% so that would equate to a difference of 19 goals per year during 5v5 ZS adjusted situations. The difference between the 5th best and 5th worst team in save percentage is 1.5% which equates to a 22.5 goal difference. These are not insignificant goal totals and they are likely driven solely by the percentages.

Now, how does this equate to differences in shot rates? If we take the team with the 5th highest shot rate and apply a league average shooting percentage and then compare it to the team with the 5th lowest shot rate we would find a difference of 17.5 goals over the course of a single season. This is slightly lower than what we saw for shooting and save percentages.

What is interesting is this (the percentages being more important than the shot rates) is not inconsistent with what we have seen at the individual level. In Tom Awad’s “What makes Good Players Good, Part I” post he identified 3 skills that good players differed from bad players. He identified the variation in +/- due to finishing as being 0.42 for finishing (shooting percentage), 0.08 for shot quality (shot location) and 0.30 for out shooting which would equate to out shooting being just 37.5% of the overall difference. I also showed that fenwick shooting percentage is more important than fenwick rates by a fairly significant margin.

Any player or team evaluation that doesn’t take into account the percentages or assumes the percentages are all luck driven is an evaluation that is not telling you the complete story.

 

Jan 252013
 

The last few days I have been looking at the percentage of a teams ice time for a given situation that a particular player is on the ice for.  So for instance, what percentage of the Leafs 5v5 even strength ice time was Joffrey Lupul on the ice in games in which Joffrey Lupul played. When I write a new program to calculate these numbers I need to to some testing to make sure the results are correct.  The first test is always the standard sniff test.  When the program runs I look at the output and ask myself “does the output make sense?”. When I first looked at the output the other day one of the numbers surprised me so much that I had to do some double checking to make sure it made sense. That number was the percentage of his teams power play ice time that Ilya Kovalchuk was on the ice for. That number was 87.25%.

That’s insane I thought so off to NHL.com to check and see if it could be at all possible. I first checked and noticed that the Devils had 439:59 minutes of PP ice time last year, including 420:36 minutes of 5v4 ice time. Next I checked out much PP ice time Kovalchuk had last year and see that he had 379:08 minutes of PP time. I do not know his exact 5v4 PP ice time numbers but 379:08 is about 86% of 439:59 so my calculation of Kovalchuk being on the ice for 87.25% of his teams PP ice time is perfectly within reason.

To me this seems like a crazy high number.  It means for every 2 minute penalty Kovalchuk is on the ice for 1:44 of it. That just makes me say “WOW!” but Kovalchuk is not alone in getting big PP minutes.  Here are some other players who have played in >70% of his teams 5v5 PP minutes (in games he played in) over the past 5 seasons.

Player 5v4 TOI%
Ilya Kovalchuk 87.25%
Alex Ovechkin 83.08%
Mike Green 76.86%
Mark Streit 75.35%
Sergei Gonchar 74.76%
Evgeni Malkin 73.83%
Sidney Crosby 73.01%
Dan Boyle 72.78%

I knew some players played a lot of PP ice time, but that still astonishes me. Oh, and for the record, in addition to being on the ice for 87.25% of his teams 5v4 PP ice time, Kovalchuk was on the ice for 89.66% of his teams 5v4 PP goals.

On the other end of things, over the last 5 years Willie Mitchell has played a whopping 59.2% of his teams 4v5 PK ice time which is might actually be more impressive considering how much more demanding playing on the PK is.

 

Jan 242013
 

The other day I introduced a new way of visualizing player time on ice and usage and today I am taking that one step further by superimposing a players performance on those charts.

So, with the TOI usage charts I presented the other day you can see how frequently a player was on the ice in any particular situation relative to how frequently the team plays during that situation.  So, a player might be on the ice for 30% of the teams 5v5 game tied minutes.  The next logical step is to take a look at his production during those situations relative to his teams production. If a player is on the ice for 30% of his teams 5v5 game tied minutes but he was only on the ice for 25% of the teams 5v5 game tied goals, that isn’t a good thing.  The team under-produced during his ice time relative to when he was not on the ice. We can also do the same for goals against and the resulting chart might look like this one for Zdeno Chara over the past 5 seasons.

The blue is Chara’s TOI usage percentages, the green is his goals for percentages and the red is his goals against percentages. You will notice that I have removed special teams play. The reason for this is because GA is not significant on power plays and GF is not significant on penalty kill so the chart ends up looking odd but in theory you could include them.

In an ideal situation the red box is smaller than the blue box (give up fewer goals than expected) and the green box is bigger than the blue box (give up more goals than expected). For Chara his results are a little mixed. When trailing he is very good having more goals for than expected and fewer goals against than expected when he is on the ice. His goals against relative to his teammates rises significantly when leading. I am not certain why, but maybe it has to do with his defense pairings when protecting a lead or opposing teams pressure him more when they are trailing.

Let’s take a look at another player who has been in the news lately, for both a contract signing and an injury.  Joffrey Lupul.

Strangely, almost the opposite of Chara. Lupul’s ‘leading’ stats are better than Chara’s while Chara is better when trailing. I am thinking maybe matchups are a factor here. When leading coaches are more diligent in matching Chara up against the opposing teams top line and keeping Lupul away from the opposing teams top line. Something to investigate further.

That said though, for Leaf fans if the Leafs get a better team that spends more time leading than trailing, Lupul’s numbers should, at least according to the chart above, get better. Especially goals against numbers.

Let’s finish off with one more superstar player, Sidney Crosby.

That is the chart of an offensively dominant player. Crosby’s offense is through the roof. Like Chara though, he is much weaker protecting a lead than any other situation.

As I said in my previous post, I am not sure where I will go with these radar charts, but they seem to be a valuable way of visualizing data so when appropriate I will attempt to make use of them. For example, it might be interesting to take a look at how a players usage and performance changes from year to year. In particular it might be interesting to see how ice time and performance changes for young players as they slowly improve or older players who are on the downsides of their careers.

 

Jan 172013
 

Yesterday evening James Mirtle from the Globe and Mail posted an article on The Curious case of Tim Connolly and the Leafs.  It’s worth a read so go read it but the premise of the article is how the narrative around Tim Connolly in training camp is he had a poor year last year and he needs to perform better this year.  Makes sense from most peoples view points but Connolly tries to present a different perspective.

Connolly can be prickly to deal with and wasn’t particularly interested in talking about last season, but when pressed, you could tell he felt he did more of value than the narrative – that he’s been an unmitigated bust in Toronto – would suggest.

Here was his answer when asked (maybe for the second or third time) about needing to “rebound” this season.

“Even strength, I think I had my second highest career points last year,” Connolly said. “I’d like to improve my play on the power play and maybe play a bigger role. Penalty killing, I think, my individual percentage was 89 per cent I read somewhere. I was able to lead the forwards in blocked shots.”

He makes two points in there.  The first is that he had his second highest even strength points last year and the second was something about individual percentage was 89 percent. Lets deal with the first one first by looking at his even strength points since the first lockout.

Season Goals Assists Points
2011-12 11 20 31
2010-11 7 16 23
2009-10 9 27 36
2008-09 12 16 28
2007-08 3 20 23
2005-06 9 20 29

(Note: Connolly only played 2 games in 2006-07 so I have omitted it from the table and discussion)

Tim Connolly is actually correct.  His best even strength point total came in 2009-10 when he had 36 points followed by his 31 even strength points last year.  But let’s take a look at those point totals relative to even strength ice time.

Season ESTOI Points TOI/Pt
2011-12 940:12 31 30:20
2010-11 840:31 23 36:33
2009-10 966:41 36 26:51
2008-09 631:26 28 22:33
2007-08 603:18 23 26:14
2005-06 708:47 29 24:26

The last column is time on ice per point, or time on ice between points.  Last year he was on the ice for an average of 30 minutes and 20 seconds between each of his even strength points. This was his second worst since the locked out season. So, while Connolly was technically correct in saying that he had his second highest even strength point total last season, it was a somewhat misleading representation of his performance.

Now for the individual PK percent. It generated a bit of twitter conversation last night questioning what it actually is.

One might think it is the penalty kill percentage when he was on the ice but that seems like a strange thing to calculate.  Is it goals per 2 minutes of PK time?  Is it goals per PK he spent any amount of time killing?  I really didn’t know so I dug into the numbers deeper by looking at the Leafs PK percentages on my stats site and noticed that Connolly had the best on-ice save percentage (listed as lowest opposition shooting percentage) of any Leaf last season during 4v5 play and that save percentage while he was on the ice was just shy of 89% (88.68%). It seems that maybe what Connolly meant to say was that he had an on-ice PK save percentage of 89%.

How good is an 89% save percentage on the PK?  Well, of the 100 forwards with at least 100 4v5 minutes of ice time last year, Connolly ranks 42nd in the league so league wide it isn’t that impressive but considering the Leafs weak goaltending it might actually be fairly good.

Here is the thing though. Single season PK save percentage is so fraught with sample size issues that it is next to useless as a stat for goalies let alone forwards.

One could evaluate Connolly based on PK goals against rate in which he came up 3rd on the Leafs (trailing Lombardi or Kulemin) but that is still fraught with sample size issues. More fairly we probably should evaluate Connolly’s PK contribution based on shots against rate or maybe even more fairly fenwick or corsi against rates. In each of those categories he ranked 5th among Leafs with at least 50 minutes of 4v5 ice time with only Joey Crabb being worse. Furthermore, among the 110 players with 100 minutes of 4v5 PK ice time last year, Connolly ranked 99th in fenwick against rate.

I don’t mean for this article to be a Connolly bashing article. I actually do think Connolly was a little misused and would probably do better with a more well defined role and not bounced around in the line up so much so in that sense I agree with the premise of what Connolly is saying. With that said though, it probably is fair to say that he didn’t have a great season and if he wants a regular role in the top six with time on the PP and PK he needs to perform better as his use of stats to attempt to show he had a good season is really just evidence to how statistics can be misused to support almost any narrative you want.  As they say, there are lies, damn lies, and then there are statistics.