Aug 092014
 

The other day over at PensionPlanPuppets.com there was a post by Draglikepull looking at zone exits by Maple Leaf defensemen for the first half of last season. If you haven’t seen it yet, definitely go read it. I wanted to compare the zone exit data to my rush shot data which I have calculated from play by play data as explained here. If we can find good correlations between zone entry/exit data and my rush shot data that would be an excellent finding because the zone entry/exit data need to be manually recorded and is very time consuming. Thankfully this is a project being undertaken by Corey Sznajder. If we can find useful correlations with data that can be automatically calculated we may not need to do this in the future and Corey can have a summer vacation next year.

Let’s first look at defensive zone exit percentage and how it correlates with rush and non-rush shots.

PlayerName RushCF/60 Non-Rush OtherCF/60 Exit%
MORGAN RIELLY 11.5 39.8 27.5
CARL GUNNARSSON 10.6 35.1 25.9
DION PHANEUF 10.1 37.9 25.5
JAKE GARDINER 11.2 37.7 24.8
JOHN-MICHAEL LILES 15.5 41.9 24
CODY FRANSON 10.5 36.9 23.8
PAUL RANGER 12.0 32.9 20.5
MARK FRASER 14.5 34.7 13.3

One thing to note is that my rush shot data is for the full season and the exit% data is for the first half of last year. Also, my rush shot data is only road data to eliminate arena bias and Liles and Fraser also includes their time with Carolina and Edmonton respectively.

Let’s look at some charts to more easily see if a correlation exits.

 

Leafs_dmen_DefZoneExitPct_vs_RushShotsFor

Ok, this is very counter-intuitive. The defensemen that have the best defensive zone exit percentage have a lower rush shot rate and a higher non-rush shot rate. On the surface this doesn’t make sense. If you are better at carrying the puck out of your own zone you should be able to generate more shots from the rush but that doesn’t seem to be the case. I think what is actually happening here is that to be able to carry the puck out of the defensive zone you have to be a skilled puck handler and if you are skilled with the puck you probably get more time in the offensive zone including more offensive zone starts and more ice time with offensive type forwards. Now, if you are not a good offensive defenseman you probably don’t get many offensive zone starts and get more defensive zone starts and maybe more importantly you play less with offensive minded forwards.

It should also be noted that Fraser is a bit of an anomaly here as his defensive zone exit percentage is well below anyone else’s and his rush shot rate is quite good. If we take Fraser out of the charts the relationship is much flatter and the correlations get weaker. We need to look at more defensemen to get more conclusive results though. Also, I think we will also find that we will get better results for forwards as I generally think it is forwards that drive the offense, not the defensemen.

Another factor in the non-relationship between defensive zone exits and rush shots for might be that often when a team exits the defensive zone they conduct a line change and maybe in particular a change in defensemen as the forwards are taking the puck up the ice. Defensemen may be able to get the puck out of their own end and initiate a rush but are on the bench before the benefits of the zone exit and follow-up rush have materialized. This could result in the lack of positive correlation between zone exits and rush shots. I need to create an “initiator of rush shots” statistic to account for this possibility.

In the comments of the pensionplanpuppets.com article Corey Sznajder provided statistics on  zone entries against each defenseman. Most defensemen would likely have significantly more control over zone entries against than they do for creating offense so we might find stronger correlations here.

PlayerName RushCA/60 OtherCA/60 Carry% Against Break-up %
MARK FRASER 18.9 44.2 71.4 7.1
JAKE GARDINER 14.9 42.4 67.7 6
MORGAN RIELLY 16.1 49.4 67.7 4.3
CARL GUNNARSSON 13.1 56.4 64.4 11.3
CODY FRANSON 14.8 46.6 64.1 5.7
JOHN-MICHAEL LILES 10.5 45.2 55.2 6.9
PAUL RANGER 14.8 49.2 54.7 17.4
DION PHANEUF 13.7 58.1 53.1 13.4

 

Leafs_dmen_RushShotsAgainst_vs_CarryInPctAgainst

Now this is a little closer to what we might expect. Those defensemen that have a high percentage of zone entries against being carry-in entries vs dump-ins give up rush shots at a higher rate while also giving up non-rush shots at a lower rate. There doesn’t appear to be any correlation between Carry In % Against and total corsi against per 60 (r^2=0.026) so it seems only the type of shot against is being impacted. I have observed that shots on the rush are significantly more difficult shots (shooting percentage on rush shots over last 7 seasons has been 9.56% vs 7.34% on non-rush shots making rush shots 30% more difficult on average) so players that can limit the frequency of carry-in rushes against and force dump-ins against instead are in fact likely to reduce average shot difficulty against.

The real counter-intuitive observation is that from a strategy/tactics point of view, it might be better to start your defensive defensemen (i.e. the ones that have the ability to limit rushes against) in the offensive zone (for the Leafs this would be Phaneuf  and Liles/Gleason last year) and start your strong offensive and weak against the rush defensemen (i.e. Rielly, Gardiner in particular) in the defensive zone . This is the opposite of what the Leafs did last season and generally opposite of what most normally consider doing. It makes sense though. When you are in your own zone you want defensemen who can get the puck and get it out and when you are in the oppositions zone you want defensemen who don’t give up high quality (often odd-man) rushes against. Defense should start in the offensive zone and offense should start in the defensive zone. The focus is generating offense on the rush and limiting the other teams ability to generate offense on the rush. It’s a bit counter-intuitive but might prove to be smart strategy.

I look forward to when the zone entry/exit tracking project gets completed and we can look at a much larger sample with more players from more teams but between that project and the rush shot data I have calculated we should gain significantly more insight into the game and how it is played. We might even come up with some new revolutionary on-ice strategies.

 

Sep 142013
 

A while back I came up with a stat which at the time I called LT Index which is essentially the percentage of a players teams ice time when leading that the player is on the ice for divided by the percentage of a players teams ice time when trailing that the player is on the ice for (in 5v5 situations and only in games in which the player played). LT Index standing for Leading-Trailing Index. I have decided to rename this statistic to Usage Ratio since it gives us an indication of whether players are used more in defensive situations (i.e. leading and protecting a lead and thus a Usage Ratio above 1.00) or in offensive situations (i.e. when trailing and in need of a goal and thus a Usage Ratio less than 1.00). I think it does a pretty good job of identifying how a player is used.

I then compared players Usage Index to their 5v5 tied statistics using the theory that a player being used in a defensive role when leading/trailing is more likely to be used in a defensive role when the game is tied. This is also an out of sample comparison (which is always a nice thing to be able to do) since we are using leading/trailing situations to identify offensive vs defensive players and then comparing to 5v5 tied situations that in no way overlap the leading or trailing data.

Let’s start by looking at forwards using data over the last 3 seasons and including all forwards with >500 minutes of 5v5 tied ice time. The following charts compare Usage Ratio with 5v5 Tied CF%, CF60 and CA60.

UsageRatiovsCFPct

UsageRatiovsCF60

UsageRatiovsCA60

Usage Ratio is on the horizontal axis with more defensive players to the right and offensive players to the left.

Usage Ratio has some correlation with CF% but that correlation is solely due to it’s connection with generating shot attempts for and not for restricting shot attempts against. Players we identify as offensive players via the Usage Ratio statistic do in fact generate more shots but players we identify as defensive players do not suppress opposition shots any. In fact, Usage Ratio and 5v5 tied CA60 is as uncorrelated as you can possibly get. One may attempt to say this is because those defensive players are playing against offensive players (i.e. tough QoC) and that is why but if this were the case then those offensive players would be playing against defensive players (i.e. tough defensive QoC) and thus should see their shot attempts suppressed as well. We don’t observe that though. It just seems that players used as defensive players are no better at suppressing shot attempts against than offensive players but are, as expected, worse at generating shot attempts for.

Before we move on to defensemen let’s take a look at how Usage Ratio compares with shooting percentage and GF60.

UsageRatiovsShPct

 

UsageRatiovsGF60

As seen with CF60, Usage Ratio is correlated with both shooting percentage and GF60 and the correlation with GF60 is stronger than with CF60. Note that the sample size for 3 seasons (or 2 1/2 actually) of 5v5 tied data is about the same as the sample size for one season of 5v5 data (players in this study have between 500 and 1300 5v5 tied minutes which is roughly equivalent of how many 5v5 minutes forwards play over the course of one full season).

FYI, the dot up at the top with the GF60 above 5 is Sidney Crosby (yeah, he is in a league of his own offensively) and the dot to the far right (heavy defensive usage) is Adam Hall.

Now let’s take a look at defensemen.

UsageRatiovsCFPctDefensemen

UsageRatiovsCF60Defensemen

UsageRatiovsCA60Defensemen

There really isn’t much going on here and how a defenseman is used really does’t tell us much at all about their 5v5 stats (only marginal correlation to CF60). As with forwards, defensemen that we identify as being used in a defensive are not any better at reducing shots against than defensemen we identify as being used in an offensive manner.

To summarize the above, players who get more minutes when playing catch up are in fact better offensive players, particularly when looking at forwards but players who get more minutes when protecting a lead are not necessarily any better defensively. We do know that there are better defensive players (the range of CA60 among forwards is similar to the range of CF60 so if there is offensive talent there is likely defensive talent too), and yet coaches aren’t playing these defensive players when protecting a lead. Coaches in general just don’t know who their good defensive players are.

Still not sold on this? Well, let’s compare 5v5 defensive zone start percentage (percentage of face offs taken in the defensive zone) to CF60 and CA60 (for forwards) in 5v5 tied situations.

DefensiveFOPctvsCF60

Percentage of face offs in the defensive zone is on the horizontal axis and CF60 is on the vertical axis. This chart is telling us that the fewer defensive zone face offs a forward gets, and thus likely more offensive face offs, the more shot attempts for they produce. In short, players who get offensive zone starts get more shot attempts.

DefensiveFOPctvsCA60

The opposite is not true though. Players who get more defensive face offs don’t give up any more or less shots than their low defensive zone face off counterparts. This tells me that if there is any connection between zone starts and CF% it is solely due to the fact that players who get offensive zone starts are better offensive players and not because players who get defensive zone starts are better defensive players.

You might again be saying to yourself ‘the players who are getting the defensive zone starts they are playing against better offensive players so doesn’t make sense that their CA60 is inflated above their talent levels (which presumably is better than average defensively)?  This might be true, but if zone starts significantly impacted performance (as would be the case if that last statement were true), either directly or indirectly because zone starts are linked to QoC, then there should be more symmetry between the charts. There isn’t though. Let’s look at what these two charts tell us:

  1. The first chart tells us that players who get offensive zone starts generate more shot attempts.
  2. The second chart tells us that players who get defensive zone starts don’t give up more shots attempts against.

If zone starts were a major factor in results, those two statements don’t jive. How can one side of the ledger show an advantage and the other side of the ledger be neutral? The way those statements can work in conjunction with each other is if zone starts don’t significantly impact results which is what I believe (and have observed before).

But, if zone starts do not significantly impact results, then the results we see in the two charts above are driven by the players talent levels. Knowing that we once again can observe that coaches are doing a decent job of identifying offensive players to start in the offensive zone but are doing a poor job at identifying defensive players to play in the defensive zone.

All of this is to say, NHL coaches generally do a poor job at identifying their best defensive players so if you think that guy who is getting all those defensive zone starts (aka ‘tough minutes’) are more likely to be defensive wizards, think again. They may not be.