PDO 3 - On Ice Shooting
- tmlblueandwhite
- Dec 24, 2022
- 5 min read
Updated: Jan 28, 2023
INTRODUCTION
Forwards tend to have higher shooting percentages (average 10.2%) than on-ice shooting percentages (average 8.0%)
On-ice shooting percentage (the team’s shooting percentage with a given player on the ice) isn’t a terribly repeatable skill.
SHOOTER TALENT REGRESSION
It’s hard to draw any conclusions there.
This “talent” regresses 71% to the mean
Only six forwards were able to exceed their expected shooting percentage by 1.5 standard deviations in both even and odd shots
a shooter is basically a shooter
SHOOTING TALENT AND SHOT QUALITY
(Oct 2011)
It is unfortunate that so many people have the misconception that shooting talent and shot quality doesn’t matter. It is not true.
I’m not denying that there’s a talent here – Tom Awad convinced me. The problem that you have is that most players aren’t Moens or Crosbys. They fall somewhere in between. We’re talking about the guys in the middle of the league, the vast majority of whom are in some statistically indistinguishable blur between 7% and 8.5%
It may be fair to say that only about ~10% are true outliers, but the outliers are the players we want to be most interested in. It’s the outliers that GMs should try to acquire or avoid.
NHL GM’s need information about the other 90% of players,
ON-ICE SH% AS A PLAYER TALENT
We already know that players can impact their own shooting percentage either through positioning (e.g. Andrew Brunette in front of the net) or skill
But can players impact the overall shooting percentage of every player who’s on the ice with them?
Bottom line: our bread-and-butter at this site is betting against continued high shooting (and save) percentages.
ON-ICE SH% AS A TALENT
(Oct 2011)
Players do in fact have the ability to drive or suppress shooting percentage and thus we must consider shooting percentage, in addition to corsi,
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.
The good players who have well-defined roles don’t see near the same variation in their on-ice shooting percentages.
PDO REGRESSION – WHY WE SHOULD IGNORE SHOOTING
for example, pdo through the first 1000 shots regresses 87% to the mean over the rest of the season – a team with a 1030 pdo through 1000 shots expects a pdo of 1004 for the rest of the season.
Basically, whatever you think you know about your team’s supposed ability to maintain high shooting and save percentages, they are very likely to crash back to league average regardless of how many shots you’ve observed.
ON-ICE SH% IS SUSTAINABLE
(April 2012)
Shooting percentage is a talent, is maintainable, and can be used as a predictor of future performance
shooting percentage is persistent and a reasonable predictor of future shooting percentage.
Both on-ice shooting percentage and on-ice fenwick for rates are somewhat reasonable predictors of future on-ice goal for rates with a slight advantage to on-ice shooting percentage
Past goal rates are the best predictor of future goal rates and thus, in my opinion anyway, the best player evaluation tool.
For all those players where we have multiple seasons worth of data (or at least one full season with >~750 minutes of ice time) for, using anything other than goals as your player evaluation tool will potentially lead to less reliable and less accurate player evaluations.
As for the defensive side of the game, I have not found a single reasonably good predictor of future goals against rates, regardless of whether I look at corsi, fenwick, goals, shooting percentage or anything else.
There are far fewer players that truly focus on defense and thus goals against is largely driven by the opposition.
Yes, over half a season shooting percentage is useless, but the majority of players we have far more than half a season of data to work with.
Overall the importance of shooting percentage and fenwick are probably pretty close to equivalent
Where there isn’t much talent is in influencing the shooting percentages of your teammates. (That is, the portion of on-ice shooting percentage that is not due to your own shots.)
INVESTIGATION INTO TEAM SH%
Compared to PDO or team save percentage, team shooting percentage does exhibit a much stronger gravitational pull towards the expected long-run mean
team shooting percentages are randomized over the long-term
Team shooting percentages are seemingly random, and we should expect those to regress to league average over the long term. But we’ve also seen that team save percentages are not random, and can be sustained at high or low levels. Expecting PDO (a combination of the two) to regress to league average, therefore, is misguided.
SH% REGRESSION
the correlation between their on-ice shooting percentage over the first three years and the next three years is only 0.33.
So our simple statistical rules tell us that if all we know is a guy’s on-ice shooting percentage over a ~3000-minute sample, our best guess for what he’d do in the future would be to take that number and pull it back 67% of the way towards the average shooting percentage.
If you take a guy with an 11% on-ice shooting percentage in the first three years, the best-fit estimation of his next three years isn’t 11%; it’s (0.3485 * 11 + 5.3525) = 9.2%. Coincidentally enough, this is almost exactly 67% closer to the mean than the starting value was.
SH% REGRESSION - GOALS
Regardless of sample size, defenseman on-ice shooting percentage is essentially completely irreproducible.
So save percentage is also essentially wholly irreproducible for defensemen, and failing to account for that weakens the analysis dramatically regardless of sample size.
The range of shooting percentage talent at forward is much larger, and so persistent differences between players are observed.
There is a relationship between ice time and shooting percentage for forwards; a good shooter is likely to play with other good shooters, and their line is likely to get more than average ice time. So we should be able to do better than just regressing every forward towards the overall average shooting percentage.
For any given player, we start with his on-ice shooting percentage in the first three years. We use his TOI to read from the first plot what the mean is for players like him, and we use his sample size to read from the second plot how far to regress towards that mean. That gives us an estimate of his future shooting percentage, which we multiply by his shot rate to project his future goal rate.
HOW MUCH SKILL EXISTS IN ON-ICE SH%
teams can sustain high shooting percentages
players have the ability to increase their teammates shooting percentage while they’re on the ice; and second, that because of this we can conclude that team shooting percentage isn’t random.
forwards seem to have at least some ability to influence their teammates shooting percentage
What we see also makes a lot of sense intuitively – forwards have more control over the shots coming off of their own sticks, but we expect that they should have at least some ability to create scoring opportunities for their teammates.
this really underscores how little control defencemen have once the puck leaves their sticks.
We needn’t ignore shooting percentages, but rather we need to keep in mind that bounces can take a long while to even out
ON-ICE SH% BY POSITION
(July 30, 2015)
On-ice shooting percentage is an excellent descriptor of what’s occurred in the past, but a poor predictor of what will occur in the future.
League-wide, you’re better off regressing a player’s on-ice shooting percentage 67% towards the league average if you want to guess what he’ll do going forward.
Defencemen have almost zero say when it comes to conversion rates.
Wingers might have a slice of control over their on-ice shooting percentages. Still, there’s not a whole lot here, and we’ll see pretty considerable variation over time.
That brings us to centres – players who chip in on goal-scoring and act as the key distributors and playmakers of the team.
It doesn’t appear as though each position should be treated equally. Defencemen have virtually zero control on whether or not his teammates convert at a high or low rate. Wingers have little. Centres have a little more. Regression is inevitable for all three positions, but the degree to which we should regress each player may differ.
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