The Puck Stops Here
Kesler’s Defensive Goals Versus Threshold
by PuckStopsHere on 09/07/10 at 12:30 AM ET
Comments (5)
When I listed top 20 forwards by defensive goals versus threshold, one player who is conspicuous by his absence from the list is Ryan Kesler of the Vancouver Canucks. Kesler has been a nominee for the Selke Trophy in each of the last two seasons. He is considered one of the top defensive forwards in the NHL. Why didn’t the goals versus threshold system find him?
Ryan Kesler scored 75 points with the Vancouver Canucks last year. That made him their third highest scorer (behind the Sedins), but his +/- rating (which is an important number in the defensive portion of the goals versus threshold system) was only a +1. This was tenth highest among the Vancouver Canuck forwards and well behind team leaders Daniel Sedin and Christian Ehrhoff, who were +36’s.
This shows the problem of relying on +/- ratings. Kesler does not have a particularly good one when compared to other Vancouver Canuck players, but that number is not evidence of poor play. In fact, Kesler was one of the best defensive forwards in the NHL last season. One of the strongest ways to show this statistically is with Kesler’s team and zone adjusted Corsi rating, which is fourth highest in the NHL last year.
The fact that Kesler can have a good Corsi relative to his team, but a poorer +/- shows that Corsi is a better measurement than +/-, at least in this case. However, it is only after adjustment that Kesler rises to near the top of the NHL. Ryan Kesler played a tough role with Vancouver that involved a lot of defensive zone starts. In fact, Kesler had the highest total of defensive zone starts minus offensive zone starts. This is part of the reason Kesler’s +/- rating was not so strong. It is easier to be scored on and not score yourself if you consistently start in the defensive zone. Despite his tough zone starts, Kesler and his team tended to possess the puck and create chances in the offensive zone at a rate far above what would be expected from the way he was used.
Ryan Kesler is one of the best defensive forwards in the NHL. It is a reasonable argument to suggest he might be the best in the league, yet the defensive goals versus threshold system completely failed to find him. He is ranked as the 133rd best defensive forward at 2.3 goals above threshold. This is a failure of the system. This failure is because it uses +/- to attempt to rate defensive goals versus threshold. A far better start would be using Corsi ratings that are adjusted for zone starts. This would require a significant rethinking of the defensive portion in the goals versus threshold system. Its failure to find Ryan Kesler as a defensive forward is an embarrassment.
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Tags: Ryan+Kesler, Vancouver+Canucks,
Comments
Have you played with any calculation adjustments that would replace the plus/minus ranking with the adjusted corsi?
I’d like to see where Kesler stacks up against Zajac and Staal under that condition.
Posted by J.J. from Kansas on 09/07/10 at 12:52 AM ET
I gave the wrong link. I have now replaced it with the correct link that includes only forwards. Ryan Kesler is 133rd among forwards alone (defencemen excluded) in this system.
I am not entirely sure how to best incorporate Corsi which is adjusted for zone starts into this system accurately. The first trick is trying to pull out defence and not offence from this system and further, figuring out the threshold level to subtract off and incorporate it properly with the other defensive measures used. I am sure that trying this even in a rather arbitrary method cannot make this system any worse and would likely improve it.
I will play with it and post something if it gives anything meaningful, but first I am not finished the whole goals versus threshold system.
Posted by PuckStopsHere on 09/07/10 at 01:03 AM ET
Thanks for the correction. I look forward to seeing what you come up with to try to correct the system.
I know it seems a bit backwards to try to play with the numbers until you get a ranking system that makes players fit what you already think, but that may be the only way to do it. You’ll find rare arguments that say that Kesler doesn’t belong near the top of the list, so it may take a bit of trial and error. Good luck.
Posted by J.J. from Kansas on 09/07/10 at 01:11 AM ET
The goals versus threshold system is at best an approximate value for players. In some cases, the approximation is better than others. Ryan Kesler’s defensive value is a glaring breakdown of the approximation. Fixing the system so that it shows Kesler as a top defensive forward, without dropping any other top defensive forward from the top or picking out forwards who are not especially strong defensively, but may have strong Corsi ratings (Alexander Ovechkin is the obvious example), will improve the approximation. However, in the end, we want a system that has a strong theoretical grounding, if this is possible.
Improving an approximate system might lead to figuring out that system, but you cannot get there with an approximate system. At some point, a new system that is not approximate is needed - assuming that is possible in the first place.
Posted by PuckStopsHere on 09/07/10 at 01:26 AM ET
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That link goes to a story you did where you listed the top 20 defensive players. Only two people on that list were forwards and you explained in that article that the system is set up specifically to value defensemen above forwards.
Assuming that change, does it also change the meaning of this sentence?
Is Kesler really the 133rd best defensive forward by this rating or the 133rd best defensive player? There could be a very large difference in these two meanings.
Posted by J.J. from Kansas on 09/07/10 at 12:50 AM ET