Wednesday, July 30, 2008

Penalty Kill +/-

In this summer's sabermetrics and hockey posts I have been discussing +/- ratings so far. I have shown two ways to adjust +/- ratings between teams: one as a rate stat and one as a counting stat. One problem with this analysis that prevents meaningful sabermetric discussions of defence is that penalty killing is not included in standard +/- ratings. Penalty killing is an important defensive function and as such should be measured, but it cannot be done starting with a traditional +/- rating.

One solution, which is credited to Gabriel Desjardins at behind the net is to treat penalty killing situations exactly the same way you treat even strength ones when calculating an on/off ice adjusted +/- which I have been calling a rate stat +/- adjustment. Obviously, individual players will have worse on ice +/- ratings in shorthanded situations. They will also have worse off ice +/- ratings. In the end, the difference between the two can be used as a ranking.

The main problem is sample size. Players do not spend a lot of time penalty killing in a season. The effect of one goal on a player's ranking is significant, so exact player ranking order needs to be viewed with caution, but it should be easy to see who the best penalty killers and who the worst ones are.

In order to solve the inconsistencies of one and two man advantages (and 4 on 3 power plays), only 5 on 4 situations are included in these numbers. The others do exist, but are so rare that it is hard to gather any meaningful statistics from them. Only players who spent at least 60 minutes killing penalties are listed in these rankings. This removes the problem of a player who killed one penalty all season "leading" in the rankings and has us including only those players who played enough time to have somewhat meaningful statistics.

Here are the top 10 players in their adjusted short handed +/- rating last season:

Top 10 Adjusted 4 on 5 Penalty Kill +/- Ratings 2007/08
RankPlayerTeamOn Ice +/- Off Ice +/- Adjusted +/-Minutes 4 on 5
1Sergei ZubovDal1.34-4.936.27134:47
2Trevor LindenVan-1.20-6.365.1699:43
3Marc SavardBos-1.88-6.885.0063:38
4Dennis WidemanBos-3.43-8.164.73227:37
5Carlo ColaiacovoTor-4.80-9.384.5862:26
6Chris KunitzAna-1.60-5.784.1875:26
7Andrew CoglianoEdm-0.92-4.984.0665:36
8Lasse KukkonenPha-1.80-5.744.0699:38
9Alexei KovalevMon-2.19-6.123.93109:53
10Zdeno CharaBos-4.17-8.103.93258:43

This list is led by Sergei Zubov, who amazing was on the ice for more goals for than against while short handed. He is followed by Trevor Linden, who was a good penalty killer despite a dropoff in the rest of his game. Then comes Marc Savard, who is not known as a defensively responsible player. Dennis Wideman is another Boston player who comes next. Carlo Colaiacovo was a successful penalty killer for the Leafs. Chris Kunitz did a very good job in Anaheim, despite not being one of their more famous defensive forwards. Andrew Cogliano appears on this list as a rookie, which is a sign of maturity beyond expectation. Lasse Kukkonen shored up the Flyer defence on the penalty kill. Alexei Kovalev did well with Montreal and is not primarily useful as a scorer. Zdeno Chara is the final player on this list.

Here are the 10 worst adjusted penalty kill +/- ratings from last year:

Worst 10 Adjusted 4 on 5 Penalty Kill +/- Ratings 2007/08
RankPlayerTeamOn Ice +/- Off Ice +/- Adjusted +/-Minutes 4 on 5
1Mats SundinTor-13.27-5.44-7.8368:05
2Jason WardTB-8.73-3.32-5.41150:53
3Steve BeginMon-8.83-3.76-5.0788:26
4Steve OttDal-6.41-2.13-4.28168:38
5Jarred SmithsonNas-6.17-1.91-4.26204:07
6Andy WozniewskiTor-8.95-4.79-4.16107:02
7Bryan SmolinskiMon-7.68-3.64-4.04109:26
8Kevyn AdamsChi-7.12-3.16-3.9667:30
9Dave BollandChi-6.60-2.64-3.9672:32
10Jim SlaterAtl-9.39-5.46-3.9382:48

Mats Sundin may be a star at even strength, but he did not do well on the penalty kill. The remainder of the list after Sundin is not nearly as big name players. Jason Ward, Steve Begin and Steve Ott are next. Jarred Smithson makes this list and worst 20 at even strength. Andy Wozniewski, Bryan Smolinski, Kevyn Adams, Dave Bolland and Jim Slater round out the list of inept penalty killers.

One piece of being able to rate individual defensive play sabermetrically is rating play on the penalty kill. Although there are limited amounts of time spent killing penalties, making for significant noise in the statistics, this can be done using on/off ice adjusted penalty kill +/- ratings. This method is successful to differentiate good and bad penalty killers.

Best of the stat posts so far, I think.
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