On-ice Shooting Percentage as a Talent
There has been an interesting discussion of on-ice shooting percentage at Tyler Dellow’s mc79hockey.com. I have argued that we need to look at on-ice shooting percentage as a talent, and not something that just happens randomly while others have largely dismissed it. One person in particular is Gabe Desjardin’s who has a followup post on his blog largely dismissing its importance.
In his blog post Gabe first discusses Gaborik’s value just considering his on-ice shooting percentage.
So are these totals 75% skill then? Let’s do a quick check on how many goals that skill would be worth: 1000 on-ice shots/season * 2.5% above mean * 75% = 18.75 goals above average. Double that to get to an approximate replacement level of 37.5 goals or just over six wins. The current price for one win on the free agent market is roughly $3M, so we’d estimate Gaborik’s offensive value at more than $18M.
Gabe doesn’t believe any one player could be worth $18M based just on shooting percentage so he tries to shoot a hole in that by looking at 2yr vs 2yr regression.
Needless to say, anytime you come up with a metric that says a player should get paid $18M, you have to go back and check your math. I did that by splitting the last four years into two two year periods (2007-08/2008-09 vs 2009-10/2010-11) and comparing on-ice shooting percentage among players who had 1000+ on-ice shots in each period. I found that player on-ice shooting regressed 80% to the mean from the first set to the second, which puts Gaborik’s apparent talent closer to $5M.
Ok, so we have Gaborik’s value down to $5M. That still seems pretty large to me but Gabe dismisses that further by suggesting some of that $5M has to be attributed to his linemates, arena bias, and strangely, a players opponents (particularly at home).
This is a key point, of course, and one that may not come through when we talk about team-level effects or try to figure out the value of individual top six forwards: when a #1 line plays against a #4 line, their shooting percentage goes up relative to when they’re playing power-vs-power.
Here is the thing. The whole reason I participate in these debates is to suggest that players do in fact have the ability to drive or suppress shooting percentage and thus we must consider shooting percentage, in addition to corsi, when evaluating players. So, it amazes me when I am debating someone that is trying to minimize the ability to drive/suppress shooting percentage that they bring up such observations that a players shooting percentage will go up when they are playing weaker players (i.e. the fourth line) who I presume can’t suppress shooting percentage as well as the stronger players. There is clearly something wrong with the logic there. Players don’t have the ability to suppress shooting percentage, but fourth liners are worse at suppressing shooting percentage than first liners??
The other thing I want to discuss is Gabe’s calculation that shooting percentage regresses 80% to the mean based on his 2yr vs 2yr calculation. I won’t dispute his math because it is probably true, but I will suggest that I don’t believe that a league-wide observation can be applied to individual players. There are a number of factors that influence a players on-ice shooting percentage.
1. The quality of his linemates.
2. The quality of opposition.
3. Style of play (i.e. aggressive offensive game vs defensive style).
4. Score effects
Team building generally revolves around a small number of players. Pittsburgh has Crosby, Malkin and Staal as their core forwards, everyone else is pretty much interchangeable. Pretty much every team is like this. A lot of those interchangeable parts move from team to team or even line to line on the same team or get asked to play different roles on the same team. An injury to Kunitz and Pascal Dupuis gets bumped from the third line to playing with Crosby. For these mostly interchangeable parts there can be a lot of variation in who they play with, the team they play on, and who they play against, and the roles they are asked to play. All these factors are at play when Gabe calculates his 80% regression to the mean. The good players who have well-defined roles don’t see near the same variation in their on-ice shooting percentages. Look at the Crosby’s and Gaborik’s. They are consistently at the top of the list. Look at the Moen’s and Marchant’s and Pahlsson’s, they are consistently near the bottom of the list. The players we perceive as good offensive players are at the top of the list. The players we perceive as weak offensive players, or defensive minded players, are at the bottom of the list. That’s a talent that we must consider.