Mike Weaver’s impact on save% (and Bryce Salvador’s too)
The other day I commented on twitter that I would be happy if the Leafs signed defenseman Mike Weaver because I think he is a defensive defenseman that I think the Leafs could really use. I have thought of Mike Weaver as a premier defensive defenseman for quite some time now. I always seem to get a little flak over it but that’s fine, I can handle it. For example, as a response to my Weaver comment on twitter Eric Tulsky thought it would be prudent to point out a “flaw” in my thought process.
— Eric T. (@BSH_EricT) June 26, 2014
And of course, Tyler Dellow never passes up an opportunity to take a jab at me (or anyone who he disagrees with) took the opportunity to re-tweet it.
Now, of course I had thought of responding with a tweet to the effect of “Florida’s save percentage was probably is a bit of a factor in that regression” but I didn’t want to get into a twitter debate at that moment and I was confident I could come up with more concrete evidence. So here is that evidence.
The above chart shows the save percentage of Weaver’s team when Weaver is on the ice vs when Weaver is not on the ice including only games in which Weaver has played in (i.e. it is better than just using team save percentage for that season and also allows us to combine his time in Florida and Montreal last season). As you can see, there has only been one season in the last 7 in which his team had a worse save percentage when he is on the ice than not. That is reasonably compelling evidence. It’s difficult to say what happened that season but his main defense partners were a young Dmitry Kulikov and Keaton Ellerby so maybe that was a factor. An investigation of Kulikov’s and Ellerby’s impact on save percentage over the years may help us identify why Weaver slipped that year. It could have been a nagging injury as well. Or, it could just be randomness associated with save percentage.
Regardless of the “reason” for the slide in 2011-12 it is pretty difficult to argue that there has been significant “regression” the past 3 seasons as Tulsky and Dellow so eagerly wanted to point out as the past 2 seasons Weaver has seemingly had a significant positive impact on his teams save percentage. Since I made that statement there has been one seasons of “regression” so to speak and two seasons in support of my claim. I guess that means it is 2-1 in my favour. It continues to appear that Weaver is a good defenseman who can suppress shot quality against.
Another defenseman I have identified as a defenseman who possibly can suppress opposition save percentage is Bryce Salvador. Here is Salvador’s on/off save percentage chart similar to Weaver’s above (2010-11 is missing as Salvador missed the season due to injury).
Salvador’s on-ice save percentage has been better than the teams save percentage every year since 2007-08. Regression? Doesn’t seem to be.
To summarize, there are a lot of instances where if we simply do a correlation of stats from one year to the next or make observations of future performance relative to past performance we see the appearance of regression. In fact, the raw stats do in fact regress. That doesn’t necessarily mean the talent doesn’t exist, just that we haven’t been able to properly isolate the talent. The talent of the individual player is only a small factor in what outcomes occur when he is on the ice (a single player is just one of 12 players on the ice during typical even strength play) so it is difficult to identify without attempting to account for these other factors (quality of team mates in particular).
Possession and shot generation/suppression is important, but ignore the percentages at your peril. They can matter a lot in player evaluation.