Monday, June 29, 2009

Estimating Even Strength Save Percentages

I've been doing a bit of work lately looking at even-strength save percentages, since the evidence suggests that they do a better job of estimating team-independent performance than overall save percentages, which can be strongly influenced by special teams play and the number of special teams opportunities.

We have official even-strength performances available from since 1998-99, and one of the things I have been tinkering with is estimating even-strength save percentages for prior years based on goalie overall save percentages and special team statistics like power plays against and power play goals against.

I compiled the even-strength numbers for the consensus top 5 goalies of the official save percentage era (Roy, Hasek, Brodeur, Belfour, Joseph), and filled them out by estimating their even-strength records for the remaining years of their careers. I'm still working on getting the best fit, so these numbers will be further refined, but I believe they give a good approximation. Once again, what many people see as a "Top 3 and Lesser 2" is more probably a "Top 2 and Lesser 3", perhaps even a "1-1-3" ranking:

Dominik Hasek: .935 even-strength sv%, .914 league average, +.021
Patrick Roy: .921 even-strength sv%, .906 league average, +.015
Martin Brodeur: .922 even-strength sv%, .916 league average, +.006
Curtis Joseph: .917 even-strength sv%, .911 league average, +.006
Ed Belfour: .916 even-strength sv%, .911 league average, +.005

I also thought it would be interesting to post a breakdown of seasons by "poor", "average", "good", and "great". I defined poor as a save percentage of below 99.5% of league average, an average season as from 99.5% - 100.5% of league average, good as 100.5% - 101.5% of league average, and great above 101.5% of league average. Here is how each goalie ended up doing in each season they faced at least 500 shots against:

Hasek: 0 bad, 0 average, 5 good, 8 great
Roy: 1 bad, 1 average, 6 good, 10 great
Brodeur: 0 bad, 7 average, 6 good, 2 great
Joseph: 3 bad, 7 average, 3 good, 3 great
Belfour: 3 bad, 6 average, 6 good, 2 great

There is a consistency argument that can be made for Brodeur over Belfour and Joseph, although some of the bad seasons for the latter two guys were late-career seasons when they were clearly on the decline. Belfour also had one average season effectively spiked by getting traded to the expansion-era San Jose Sharks, who were a legitimate shot quality outlier. In addition, Brodeur almost always tended to play more minutes than the other guys did, so as such we would expect his numbers to less affected by random variations.

If we further restrict it to seasons where the goalies faced at least 1000 shots against, and were between the ages of 21 and 36 (to match Brodeur's career so far), we get the following:

Hasek: 0-0-1-6
Roy: 0-1-6-9
Brodeur: 0-6-5-2
Joseph: 0-5-2-3
Belfour: 2-4-3-2

That shows much less of a difference between the bottom three guys, particularly for Joseph who really had his game desert him in his later years.

I still find it hard to see a significant difference between Brodeur and Belfour. There's not much between them other than in the games played column, and one could argue that Belfour closes some of that gap with superior playoff results. Over a 20 year career Brodeur likely gives a team more total value, but if you had to choose one of them to play a key game for you it's pretty much a tossup.

There was also probably little to no difference between Brodeur and Joseph in terms of stopping the puck, once you put the two of them on a level playing field. Joseph didn't age gracefully, but at his peak he was probably better than Brodeur at making the first save. When taking everything into consideration, however, Brodeur has much better non-save skills and that breaks the tie.

In an all-time perspective, if one was to rate goalies based on how they actually played, not based on how well their teams did or how good sportswriters thought they were, then Brodeur should be ranked much closer to Belfour and Joseph than to Hasek or Roy. As I've said many times before, I believe it's a mistake to rank Brodeur up with the latter two, as both of them had 6-7 years of prime seasons at a level well above anything Brodeur ever reached.

I hope to post some more numbers for other goalies when I get a chance. I did manage to run the numbers for Roberto Luongo, since he has done well in similar performance measures. I know it doesn't matter anymore now that he let in 7 goals in one playoff game, thereby rendering all previous results obsolete, but Luongo has a career .929 even-strength save percentage, compared to a league average of .918, for a +.011 difference, with 5 good seasons and 3 great seasons. That puts him on a trajectory to end up somewhere around the Belfour/Brodeur/Joseph range or even a bit above, keeping in mind that Belfour and Brodeur close the gap some when you factor in their apparent shot prevention effects.


Navin Vaswani (@eyebleaf) said...

Dude...I love this blog.

JLikens said...

I'm interested in your opinion about Roy.

His save percentage -- and presumably his EV save percentage -- relative to the league average during the late 80s and early 90s was highly impressive and much better than the league average during that timeframe.

However, from the mid 90s onward, his numbers, while still well above average, were never quite as impressive.

Would you attribute this to an age-related decline, or the fact that Canadiens of that period were an excellent defensive team in an era where team effects on (EV) save percentage were relatively more pronounced?

Anonymous said...

Yea I was going to say the exact same thing. Roy's numbers are pretty similar to Brodeurs if you compare the time they were both in the league. Yet Roy is given the advantage because he was fortunate to play on a good defensive team in an offensive era? Thats really the thing that "supposedly puts him on top", benefitting froma good defensive team and that terrible "league average" save % early in his career. Why couldnt he keep it up on better teams in a much more defensive era? Without shot quality data, it would be the equivalent to looking back at Nick Backstrom 20 years from now and marveling at his extremely high save percentage compared to league average.

Otherwise I'll leave it at that. No need to point out the obvious error in drawing conclusion solely off of one statistic.

The Contrarian Goaltender said...

My opinion about Roy is that he was a very good goalie, but that he is a little overrated because of his teammates. I have him rated as #2 to Hasek in the save percentage era and #4 all-time.

I'm pretty sure Roy benefitted from the teams that he played on. His backups put up some very nice numbers in both Montreal and Colorado, which suggests that his team context was favourable. Some of that was team discipline (the Montreal teams took very few penalties, similar to Brodeur's later teams in New Jersey), but I wouldn't be surprised if Montreal and/or Colorado were shot quality outliers that might well add +.003-.005 to a goalie's ES SV%. His strong teams also helped Roy put up the huge playoff numbers that he is remembered for. Roy won only 5 playoff series in his entire career where his team did not have home-ice advantage.

I'm not exactly sure what kind of team-to-team variance there was in even-strength save percentage in the 1980s (that's on the to-do list), but it makes sense to me that there would be more than today.

Having said that, Roy's career path doesn't look unusual to me - he peaks in his mid-20s, and he drops to a lower but still consistent level of play over his later 20s and 30s. That's pretty standard. So I'd say most of it can be attributed to typical aging, with the height of the peak likely exaggerated somewhat because of the defensive strength in Montreal.

"Roy's numbers are pretty similar to Brodeurs if you compare the time they were both in the league."

That's not true, unless you're talking about things like wins and shutouts. In terms of save percentage, Roy always had Brodeur beat.

Here are my estimated even-strength save percentages for 1994 to 2003:

Hasek, .938
Roy, .928
Brodeur, .920
Joseph, .919
Belfour, .916

It is, once again, stunning to see how much Hasek owned that period, but Roy was quite clearly the next best guy.

Anonymous said...

I agree with you on Brodeur/Belfour/Cujo but I think the second-ranked goalie should be J-S Giguere, not Roy. "St. Patrick" never played on a crap team in his life the way Giggy did for several years. Yes, Giggy had a couple of mediocre years (2006 and 2009), but his injuries and personal-life issues should be factored in for this.

The tiebreaker between him and Luongo should be Giggy's two excellent postseason runs (one of which is probably the most phenomenal run of all time).

The Contrarian Goaltender said...

Giguere's even-strength numbers are pretty good. He has a career even-strength save percentage of .926, when league average has been .918. That's +.008, which is not too far behind Luongo. Given Luongo's higher peak, younger age and games played advantage I certainly wouldn't put Giguere ahead of him, but those are very good results. I've always said I thought Giguere was a good goalie.

Still, rating Giguere above Patrick Roy is flat-out wrong. It doesn't matter whether a goalie plays on a good team or a bad team, it matters how well they play given their situation. I often sing the praises of overlooked goalies on poor teams, but they are not better just because their teammates are weak, they are only deserving of praise if their performance is strong. The difference between Roy's teams and Giguere's teams is not as large as the difference in performance between them.

Even if you take out Roy's peak, he still comes out far ahead of Giguere and the other goalies. Take 1992-93 to 2002-03, for example, which doesn't count any of Roy's Vezinas or save percentage titles, and Roy is still at .926 when league average is .912. And that is in more games than Giguere has played in over his career. Roy has an excellent peak, excellent longevity, excellent consistency, and excellent playoff performances, which is why pretty much everyone who rates goalies puts him near the very top of the list. And if you place a heavy weighting on individual playoff runs, well you might have heard a little something about Roy in 1986 or 1993.

Anonymous said...

Don't get me wrong, Roy's runs in 1993, 1996, and 2001 (I haven't studied '86) were amazing, but the fact is that he was on great teams each and every time, and that has to be taken into account.

Do you think that Roy could have gotten a garbage team into the playoffs and taken them on a Cinderella run? It's hard to say since he never played on one but the goalies I consider #1 and 2 in the modern era, Hasek and J-S, both have, and both won the Cup the first year they got on a truly good team.

The Contrarian Goaltender said...

"the fact is that he was on great teams each and every time, and that has to be taken into account."

I agree, but you're not "taking it into account", you're simply writing it off. The proper way is to include a team adjustment, not to just say it doesn't count because his teams were good. The save percentage differential between Roy and league average is almost twice that between Giguere and average. This is at even-strength, so the team adjustment is not going to huge, and even a .005 or something is going to leave Roy well ahead.

"Do you think that Roy could have gotten a garbage team into the playoffs and taken them on a Cinderella run?"

Maybe not, as very, very few goalies have ever gotten a garbage team into the playoffs and taken them on a Cinderella run. And Giguere is not one of them. The 2003 Ducks were not worse than average, they had an excellent coach, some good top end players, strong team defence and yes, good goaltending. The seasons before and after the teams were weaker, and they finished well out of the playoffs.

Having said that, Roy was clearly a better goalie than Giguere, so I'd say however likely Giguere was to do it, Roy was even more likely.

I just can't believe how much weighting you put on one playoff run. It was terrific, everyone agrees with that, but it was at a level Giguere never reached before that, has never reached since, and almost certainly will never reach again. So why do you keep using it as your proof of Giguere's greatness?

Giguere's career playoff save percentage other than 2003 is a very mediocre .907. I guess those other games don't count? Disparaging Patrick Roy's career and ranking him behind Giguere simply because Roy's teams were better and because Giguere was rolling sixes for 14 straight games in 2003 is completely at odds with the way I go about evaluating goalies.

Anonymous said...

Show me where I disparaged "St. Patrick". The guy was unbelievable and had a very long prime with no real bad years whatsoever. Nonetheless, he never played on any bad teams either. Your whole blog is dedicated to revealing the truth that team effects matter more than goalie skill in determining winning, losing, and team strength.

As I have said before, the closest analogy to Giguere is Hasek. In fact, J-S even employed some Hasek-like moves during his '03 run. At this point, I will face the reality that Giggy has been rather more vulnerable than most netminders to injuries and mental funks brought on by personal stress (i.e. the medical condition of his infant son, the death of his father, etc.) come postseason time. But Hasek was really no different (how about explaining 1997 to us, when the Dominator completely flaked-out and left Stevie Shields holding the bag) in that regard. Outstanding goaltenders are often flaky to the core.

I disagree with your analysis of the early '00s Ducks teams, also. The 2003 Ducks team was average at best--better than the 2002 team that scored something like 150 goals the whole year for sure, but very mediocre without Giggy's .920 save percentage. With even slightly-above average goaltending, the '03 team would have been 9th place at best--the closest analogy to the team as a whole (besides the goaltenders) would be the '99 Sabres. I also think it's a fair case to study of the phenomenon of goalie effects on the rest of the team (vs. team effects on the goalie). A lot of the reason why the '03 Ducks won the games that they did, especially in the playoffs, was the fact that the scorers had complete and total confidence that if their risky plays resulted in breakaways and odd-man rushes, the odds were overwhelmingly likely that Giggy would swallow them up.

Marginal, weak playoff teams without a lot of high-end skill pretty much have to make risky gambles of plays constantly if they are to have any chance at scoring and winning. When this is not accompanied by a great goaltender that serves as an equalizer, the result is rapid elimination (look at the late '90s/early '00s Oilers with Tommy Salo).