GOALIE EVSV% PROJECTIONS
https://www.broadstreethockey.com/2012/1/25/2730816/goalie-save-percentage-projections-even-strength
Whether you are trying to predict a guy’s overall performance or just his even strength performance, you are better off looking at his total numbers for this year than just his even strength numbers.
This is consistent with the idea that PK Sv% and ES Sv% measure largely the same talent, and that the variability of the PK Sv% comes mostly from the small sample sizes.
Overall save percentage will give the best outcomes if you are using only a single year to make your predictions.
Up to about 100-150 games of career numbers, overall save percentage and even strength save percentage perform similarly.
After 150+ games, even strength save percentage is the better predictor of a goalie’s future success.
USING PLAYOFF DATA TO BETTER PROJECTIONS
(Aug 7, 2021)
We actually see a relatively large improvement in how predictable a goalie’s regular season results are when using playoff statistics too.
if you are going to evaluate them in a predictive sense, include his playoff results if he has any.
GOALTENDER MARCELS
NHL STATS PROJECTIONS
Past history shouldn’t affect our projections as much as the most recent results, but it’s not meaningless either.
We look at what system of weights on each of the previous years would have come up with the answer that most closely matches the actual outcomes.
If I just try to predict the coming season instead of the next three, I get a 100-70-50-10 weighting.
The result is that recent performance matters a bit more than older data, but the older data is still quite significant
FORECASTING FUTURE GOALIE PERFORMANCE
when forecasting future performance, but rather to take a weighted average in which we place greater importance on more recent data.
if a more complicated forecasting system can’t beat Marcel, it’s useless.
The point isn’t really to project absolute SV% for the next year as much as it is to project the quality of goalies over the next three years. I think this seems like a pretty solid way of doing so.
UPDATING GOALIE MARCELS
due in large part to the aging adjustment, finding goalies in free agency to act as a multi-year starter is basically a losing play.
the best way to obtain goalies is through development and early signings – the UFA market sucks for long term goalie stability due to aging (not to mention the best goalies being locked up through their better years).
MARCELS TO FORECAST PERFORMANCE
Marcel forecasts model a player’s true talent level and fluctuations away from those forecasts can be largely attributed to randomness.
MARCELS PROJECTIONS FOR GOALIES
Traditionally the weights are 5/4/3 but we can do a little better.
We get 10/8/3. A bit more aggressive than 5/4/3 but It seems fine to me.
these weights indicate the past two years of a player’s performance matters a lot for projecting next years HSv%.
Low/Mid Sv% contain a lot less skill than High Sv% making one year of data a really bad judge of talent.
HSv% is the most important component. This is because it’s where most of the spread in skill is and because it’s the fastest one to reach a signal.
BAYESIAN APPROACH TO PREDICTING SV%
BAYESIAN APPROACH TO ANALYZING GOALIES
ESSV% tends to be very inconsistent especially for goalies who have faced a relatively small number of shots.
If we know ESSV% is fairly inconsistent, and we know that extremely high or low save percentages typically regress heavily to the league’s mean ESSV%, perhaps we could develop a metric that is more conservative and less subject to large fluctuations.
The more data we get, the less influence the prior has, and the more influence the data has. This method is automagically regressing Luongo to the mean by an appropriate amount based on how much data there is.
GOALIE PERFORMANCE PREDICTIONS
So let’s say we have a goalie who’s posted a strong save percentage in his rookie year and we want to figure out how likely he is to keep it up. The best way to handle situations like this is usually with Bayesian analysis,
This analysis doesn’t use anything except the goalie’s NHL history to date, and in the absence of data to the contrary, it assumes that the goalie is league average
Still, it’s worth bearing in mind that while NHL performance is the most useful evidence of how good a goalie is, it’s not the only factor.
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