STUMBLING ON WINS
you have to regress the goalie 75% towards the mean.
Now, to simplify, suppose the variance of SV% consists of only talent and luck. A full-time goalie plays about 3,500 minutes. In my regression, it turns out that you get 1 part talent to three parts luck (that’s where the .25 comes from: 25% of the total is talent).
exactly half a full-time goalie’s observed difference from the mean is real, and will be repeated next season; if a goalie is .020 better than average this year, expect him to be .010 better than average next year.
I don’t think you can say “there’s little difference between goalies” at all.
a good part of what we see of a goalie’s performance is real.
But, does all this mean that “there’s little difference between goalies?.
A goalie who’s one SD above average will have a save percentage .0055 better than average. A goalie who’s two SDs above average will be .011 better than the mean.
the SD at 9 goals for now, which is comparable to that of a top forward in the league (8 – 10 goals).
NO SKILL DIFFERENCE BETWEEN GOALIES
(May 14, 2010)
What we see is that, for almost three-quarters of the goaltenders in the NHL, their performance is almost indistinguishable from one another.
In practice, the assumption that there is little skill difference between most NHL goaltenders is correct. You can rarely count on your goaltending to win you a game or a series because Brian Boucher can outplay Martin Brodeur over 7 (okay, 5) games, but there is still some difference.
WHY THE GOALIE MARKET IS SO STRANGE
Goaltending is the most important ‘easily’ controllable portion of building a team – goaltending is an enormous factor in determining who the good and bad teams are – with well-below-average goaltending, your chances at the playoffs are based on shooting luck and OT/shootout luck. It’s not possible to be ‘good’ enough in today’s NHL to overcome horrendous goaltending.
Goaltending is really difficult to evaluate year to year – However, that’s the problem – while goaltending is vital to a team’s success, it’s also largely unpredictable.
EVALUATING GOALTENDERS
(Oct 2013)
Goaltenders can be tricky to evaluate because they are frequently the most impactful players in single games or seasons for a team.
It is extremely difficult to project goaltender performance, which thus lowers their value.
You need four full years of performance before a goaltender’s save percentage become reliable enough to evaluate due to how random save percentage is.
Even when you get years worth of data, outside of the very good and very poor goaltenders, three quarters of goaltenders in the NHL have performance that is “almost indistinguishable” when you get a reliable amount of years.
Therefore, barring extremely good or extremely bad seasons, it is almost impossible to dissect anything meaningful from single season goalie numbers with current statistics
Goaltenders in single games can swing its dynamics unlike any other position and can be among the most valuable players in the league. Save percentage is the only stat that is really useful for NHL goaltending performance, and it is really unreliable.
Once you have waited years and found out how good a goalie really is, unless you have one of the very best or very worst starting goaltenders, chances are the other 20-25 goaltenders are not all that different skillwise from each other.
GOALTENDING – BEST FRIEND OR WORST ENEMY
For those of you who are unaware, goalies can be wildly inconsistent. A goalies SV% tends to vary quite largely from year-to-year. Even better evaluators of true talent such as ESSV% or RoadSV% will rise and fall from year to year.
The basics of what I did was look at every NHL goalie who had faced about 900 shots (or about 35 games played), and regressed their save percentage 75% towards the mean.
While this helps us more or less neutralize the effects of a particularly strong or weak season by a particular goalie it doesn’t totally level the playing field, keeping individuality live and well.
GOALIES AND CONFIDENCE INTERVALS
(Oct 2014)
That’s the role a confidence interval plays: taking your sample (however big or small) and using it to tell you the values the whole population probably lies between—for a given probability. This is the process of finding out how good a goalie is: looking at roll after roll of a many-sided die to narrow down the possibilities.
The main takeaway for me is just how little we can say definitively about goalies who haven’t faced a lot of shots.
we should be a bit more cautious about assuming a goalie who played a stellar half season will keep it up in the future.
Confidence intervals are helpful in forcing us to check our expectations about unproven goalies. In the long run, they can do more to help us determine relative value than save percentage alone.
As is often said, goalies are voodoo. We would do well to remember that
GOALTENDING GAME THEORY
(April 2017)
Absolute NHL goaltender ability has continually increased for the last 30 years. However, differential ability between goaltenders has tightened. It has become increasingly difficult to distinguish long-term, sustainable goaltender ability while variations in results are increasingly owed to random chance.
This is not to say all goalies in 2016 are of equal skill levels, but they are absolutely more talented than their ancestors and fall within a smaller range of abilities. That said, outside of a top 2 or 3 guys, the top 5-10 list of goalies is a game of musical chairs, quarter to quarter, season to season.
By mixing strategies when it is wise, (when the simple block-react instantaneous move model applies) the goaltender can increase their expected save percentage—and exceed the average.
It is exceeding the average that causes goaltenders to contribute to victories, the absolute measurement of success for any goaltender.
Simply ‘playing the percentages,’ with an emphasis on blocking from the butterfly, leaves the goaltenders fate up to pure chance. No goaltender can attempt to consistently out-perform their peers by playing the percentages—at least, not with certainty. Hoping to block 90% of the net while relying on your team to limit quality opportunities will result in mediocrity.
WHY GOALTENDING IS BASICALLY RANDOM
(Aug 2020)
You can’t even predict goalie consistency in a single season (game to game).
Expecting your team’s starting goalie to have anything resembling consistency is an absolute fools errand.
This is why paying big money (especially over the long term) for a goalie is a fool’s errand. As the Panthers learned this season, it is risky to the point of insanity to bet that a starter will be able to maintain even an above-average level of play throughout a contract, let alone a high level.
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