May 172011
 

I wrote an article a few weeks ago about the offensive and defensive contribution (i.e. their HARO+ or HARD+ rating multiplied by ice time) of each position (C, LW, RW, D and G) but I have come to realize that my methodology is incorrect and thus the conclusions are incorrect (at least when looking at league-wide results).  The reason is, in my rating system contribution is evenly distributed among the 5 players on the ice so if I sum up all contributions of all players playing at a particular position I should see each position be given an equal share, and for the most part that is what I saw.  The exception being centers being given more influence and wingers less, this is because players that are listed as being centers often play the wing where as wingers are less often on the ice playing as centers.

The proper method for identifying the contribution a position has on offense and defense is not to sum up their contribution but to look at the variation observed in the players ratings for that position.  Recall that with my ratings a 1.00 is a neutral rating or an indication that the player has no positive or negative effect for that aspect of the game (offense or defense) compared to the expected level of performance when quality of competition and quality of teammates are considered.  Anything less than 1.0 implies a negative impact and anything above 1.0 implies a positive impact.  So, if a position can significantly influence offensive production then we should see a larger variance among centers HARO+ ratings.  The good players at that position will have ratings well above 1.00 and the weaker players well below 1.00.  For positions that do not have a significant impact we should see players at that position have ratings much closer to 1.00 and less variation between the best and worst players.   So, here is what we find.

HARO+ HARO+ HARD+ HARD+ HART+ HART+
Position Average StdDev Average StdDev Average StdDev
C 0.918 0.171 0.994 0.116 0.956 0.091
RW 0.927 0.162 1.001 0.096 0.965 0.084
LW 0.939 0.167 0.993 0.099 0.966 0.086
D 0.894 0.095 0.990 0.101 0.942 0.068
G 0.984 0.080 0.992 0.040

The above uses four year ratings (2007-11) and only forwards and defensemen with at least 2000 minutes of 5v5 even strength ice time and goalies with 3000 minutes were considered.  The resulting group included 122 centers, 85 LW, 103 RW, 194 defensemen and 53 goalies.

On offense, the three forward positions have significantly higher standard deviations (0.162-0.171) than defensemen (0.095) which intuitively makes sense.  It means that forwards have a greater ability to influence offensive production than defensemen which is no surprise.  Defensively the greatest variation in HARD+ occurs for centers with defensemen and wingers more or less the same a step below centers and goalies another step back again.  It is possible centers rank ahead of wingers and defensemen in part because they are the ones who take face offs and thus are a major factor in the team gaining control of the puck.

The other thing that you’ll notice is that for HARO+ the average rating is well below 1.00 for both the forwards and the defense.  This probably indicates that the big minute players are the offensive players which makes the average rating (which is ice-time neutral) well below the ice time weighted average (which in theory should be very close to 1.00).  Lets take a look at how the players rate according to total ice time.

Centers

Ice time HARO+ HARD+ HART+
>4000 min. 1.042 0.968 1.005
3000-3999 0.906 0.988 0.947
2000-2999 0.864 1.015 0.940
1000-1999 0.784 1.025 0.905

Left Wing

Ice time HARO+ HARD+ HART+
>4000 min. 1.089 0.939 1.014
3000-3999 0.987 0.990 0.989
2000-2999 0.824 1.015 0.920
1000-1999 0.760 1.036 0.899

Right Wing

Ice time HARO+ HARD+ HART+
>4000 min. 1.071 0.963 1.018
3000-3999 0.953 1.003 0.979
2000-2999 0.871 1.008 0.940
1000-1999 0.775 1.047 0.911

For the three forward positions it is clear that the top offensive players get the most playing time while players who get less playing time are slightly better defensive players.  This isn’t really a big surprise as the majority of a team’s offense comes from their top line(s).  The question is, how much does coaching/playing style influence the results.  By that I mean, would first line forwards be better defensively if they were on the third line and asked to play a defensive role as opposed to being on the first line and being asked to and expected to produce offense?  I suspect for most players the answer would be yes.  I suspect the reverse (third/fourth line guys having better offensive ratings if given first line roles) is also true, but probably to a lesser extent.

Defense

Ice time HARO+ HARD+ HART+
>5000 min. 0.923 0.988 0.955
4000-4999 0.919 0.997 0.958
3000-3999 0.871 0.998 0.934
2000-2999 0.874 0.974 0.923
1000-1999 0.864 1.025 0.944

For defensemen the best offensive defensemen still get the most ice time, though the variation is much less than seen with the forwards.  Defensive ability seems to have very little variation across ice times until you get to the lower minute players who appear to be more defensive specialists.

Goalie

Ice time HARD+
>10000 min. 1.040
>8000 min. 1.028
>6000 min. 1.012
>4000 min. 0.992
>2000 min. 0.984

As one would expect, the best goalies are given the most time in goal.  There were 9 goalies with greater than 10,000 minutes of 5v5 ice time and all had ratings over 1.00 except Tomas Vokoun whose rating was 0.978.  According to my rating system, Vokoun is a pretty ordinary goalie which means he is likely one of the more over rated goalies in the NHL because some (or most) consider him elite.  It’ll be interesting to see where he ends up this summer as a UFA and how that team performs next year.  Could Vokoun be another goalie failure in Philadelphia?  Could happen.

Dec 162010
 

In the Hockey Statistical Analysis world Tomas Vokoun is an interesting case study because depending on how he gets evaluated he either shows up as an very good goalie or in some cases a true elite goalie in the NHL.  Most ways we evaluate goalies has to do with save percentages.  We either look at overall save percentage or even strength save percentage or even even strength game tied save percentage.  Under all of these scenarios Vokoun excels to various degrees.  A recent Behind the Net Hockey Blog post asked several hockey statistic analysts to discuss “elite goalies” and Tomas Vokoun’s name came up frequently.  What is dumbfounding to me is Vokoun’s record because his won-loss record (79-80-25) is notably worse over the past 3 seasons than his backups (32-22-8).  That can’t be a sign of an elite goalie, even if his backups have been relatively good (i.e. Craig Anderson).  One may postulate it is due to facing tougher competition as backup goalies often get the to play against weaker teams or one may postulate it is just due to bad luck.  Or maybe, he just isn’t a great goalie.

Since shots totals and shooting/save percentage is often affected by game score I’ll focus on 5v5 even strength game tied statistics to balance everything out.  Over the last 3 seasons (2007-08 to 2009-10) there are 35 goalies with 1500 or more 5v5 game tied minutes.  Of these goalies, Tomas Vokoun ranks 8th in 5v5 game tied save percentage which may not be elite, but still very good.  Jonas Hiller tops the list with a .942 save % with Vokoun at .933 and Chris Osgood trails the list with a .906 save %.  So, Vokoun looks pretty good.

But, Tomas Vokoun ranks just 23rd in goals against average which isn’t great and probably average at best.  Those who are in love with fenwick numbers will note that Vokoun has the second highest fenwick against of any goalies with 1500+ 5v5 tied minutes and he gives up so many goals because Florida gives up so many shots and scoring chances.  Of course, I believe that not all shots against are equal and shot totals can be influenced by style of play as much as talent.  If you don’t believe style of play affects shot totals and scoring chances, ask yourself why there are score effects on shot/corsi totals?  The answer is depending on the score, teams play differently.  But teams play differently when the score is tied as well.  Some teams play a defense first style, even when game is tied, and others play a more wide open offensive style.  Florida, without any true elite offensive stars, probably plays more of a defensive game which would naturally lead to more shots against, but not necessarily more quality scoring chances against.

So yes, Florida gives up a lot of shots, but how good is Tomas Vokoun’s competition really.  He does play in the weakest division in the NHL and yet he can’t produce a good won-loss record.  Just looking at Vokoun’s opposition, his opponents rank dead last in goals for per 20 minutes so compared to other goalies he is playing against relatively weak opponents offensively.  His oppositions GF% (goals for / goals for + against) is also fourth worst so overall so he plays against very weak opposition in terms of scoring goals and stopping goals.  For those who prefer Fenwick, his opposition has a FF% (fenwick for / fenwick for + against) of .499, good for 27th among the 35 goalies.  So his opposition isn’t good and his performance in goals against average isn’t good either.  That isn’t a good combination if you want to be considered an elite level goalie.

How about a direct comparison with his backups.  In 2007-08 his goals against average per 20 minutes was significantly worse than Craig Anderson’s (0.949 for Vokoun, 0.538 for Anderson) while Anderson’s opponents had a slightly better goals for per 20 minutes (0.678 vs 0.671).  In 2008-09 Vokoun had a much better season giving up 0.697 goals per 20 minutes compared to Anderson’s 0.896 though Anderson played against slightly better offensive competition.  In 2009-10 Vokoun had a much better goals against than Clemmensen (0.621 vs 1.058) but played against weaker competition as well (OppGF20 of .714 vs 0.743 for Clemmensen’s opponents).  Generally speaking Tomas Vokoun had a very weak 2007-08 season but much better 2008-09 and 2009-10 seasons even though he always seemed to play against weaker offensive opponents.

In terms of my Hockey Analysis Ratings, Tomas Vokoun ranked 16th out of 35 goalies in 2007-10 HARD and 18th in 2007-10 HARD+ rankings.  Middle of the pack.  The seasonal breakdown positioned him 35th of 38 in HARD+ for goalies with 500+ minutes in 2007-08, 19th of 35 in 2008-09, and 6th of 37 in 2009-10.  So far this season he is closer to the bottom again.

Is Tomas Vokoun an elite goalie, or even great goalie?  Probably not.  He just posts good save percentages because his team gives up a lot of shots, but not necessarily quality scoring chances, and he plays against weak offensive competition.