Saturday, October 10, 2009

The Win Threshold

I am firmly against comparing goalies based on wins. This is not because wins aren't important or desirable. Wins are what every player and team wants more than anything else. What makes wins a poor stat is that every team situation is different. If every goalie played the same schedule with identical teammates in front of them, then we could just give the Vezina to the guy with the most wins at the end of the season. In real life, goalies do not compete on a level playing field.

The two most important team factors that affect a goalie's ability to win are his goal support and the number of shots he has to face. More goal support means that more of his mistakes are covered up, and facing fewer shots against means fewer opportunities to allow goals.

Last year the Detroit Red Wings had the league's best offence, scoring 3.52 goals per game. They also allowed the second fewest shots against per game with 27.7. On the other end of the scale, the New York Islanders finished second last in both goals for (2.42) and shots against (33.5) per game. Quite obviously an Islander goalie would need to be much better than a Red Wing goalie for their teams to have the same chance at winning, because he would have to make up for his team scoring one less goal per game and he would have to do it while facing an extra half-dozen shots against.

We can calculate what I'll call the "win threshold" for the goalies on each team by taking (shots against - goals for) / shots against. This gives us the save percentage that would result in the team ending up with an equal number of goals for and goals against over the course of the season. If the goalie's save percentage is above that number, the team is likely to win more than the lose, while anything below the threshold means that the team should end up sub-.500 (or sub-.550 in the shootout era).

In 2008-09, Detroit's win threshold was .873, which was the lowest in the league. The Islanders' win threshold was .928, which was not only the highest mark in the league but also the highest of any team since the lockout.

Expressed a different way, Detroit is likely to win if their opponents have a shooting percentage of 12.6% or worse. The New York Islanders are likely to win only if their opponents have a shooting percentage of 7.1% or worse. The shooting percentage against Detroit needs to be almost 80% higher than the percentage against the Islanders for the teams to have the same likelihood of winning the game.

Naturally, comparing win totals on goalies playing on the Islanders to goalies playing on the Red Wings is completely senseless. It would be like comparing two students in terms of how many course credits they attained, where the first student passes their courses if they achieve a mark of 50% or better while the second student only passes if they score 90% or higher. With that advantage, the first student is much more likely to pass his courses and achieve a higher overall number of passes. Even if the second student is exceptional and the first student is mediocre, it is likely that the first student will have a similar or better score because of their inherent advantage.

I ran the formula for every team since the 1997-98 season, including an adjustment for average league goals and shots per game.

Top 10 since 1997-98:
1. 2001 Devils, .860
2. 2004 Senators, .866
3. 2000 Blues, .867
4. 2003 Senators, .868
5. 2008 Red Wings, .869
6. 1998 Blues, .872
6. 1999 Blues, .872
6. 1998 Stars, .872
6. 2006 Red Wings, .872
10. 2001 Avalanche, .874
10. 2003 Blues, .874
10. 2009 Red Wings, .874

Bottom 10 since 1997-98:
1. 1998 Lightning, .937
2. 2002 Thrashers, .935
2. 2000 Thrashers, .935
4. 2003 Panthers, .934
5. 2002 Blue Jackets, .933
6. 2002 Panthers, .932
7. 1999 Lightning, .931
7. 2000 Islanders,. 931
7. 2004 Panthers, .931
10. 2001 Wild, .930
10. 2004 Blue Jackets, .930

If you ever wondered how Roman Turek managed to get 42 wins in a season, or how Patrick Lalime won 39, here's your answer. On the other hand, note that four of Roberto Luongo's teams show up in the bottom 10. Why didn't the Florida Panthers make the playoffs? Because the team was terrible. It had nothing to do with the goaltending.

Note that these are team totals that need to be achieved, which make it even more difficult for goalies on the worst teams than it appears at first glance. If they have a backup who plays around 20-25 games at .900, then the starting goalie would need to be at .940 or better for the team to have a goal differential of zero. Even then, the team is unlikely to make the playoffs without scoring more goals than they allow.

The average win/loss record of the teams in the top 10 list was 48-22-12. The average win/loss record of the teams in the bottom 10 was 22-46-14. What is interesting, however, is that the goaltending performance was quite similar:

Save % of top 10 teams: .905
Save % of bottom 10 teams: .904

The teams on the top list didn't win because of great goaltending or because their goalie gave them clutch saves. They won because their teams scored a lot of goals and didn't allow many shots against. Similarly, the teams on the bottom list lost because they struggled to score and allowed too many shots against, not because their goaltenders were poor. This is further proof that win totals are a team stat, and should not be used to evaluate individual goalies.

12 comments:

Scott Reynolds said...

I know that this runs contrary to your point about not using win totals to measure individual performance but do you think wins above expectation could be an effective measure for goalies in the pre-save percentage era?

The Contrarian Goaltender said...

It could be, but without shot totals it's hard to assess how good the team's defence was. In the pre-save percentage era we have to use whatever information we have available, including wins. My issue is more with unadjusted win totals, as wins aren't really that bad of a stat if we adjust for team factors.

Lawrence said...

Something in here isn't sitting right, IMO, and I don't know what exactly it is, but Roman Turek is a good example of it.

"If you ever wondered how Roman Turek managed to get 42 wins in a season, here's your answer...The teams on the top list didn't win because of great goaltending or because their goalie gave them clutch saves. They won because their teams scored a lot of goals and didn't allow many shots against."

So when we compare Turek's two seasons with the Blues in 2000 and 2001 the goals for were basically equal: '00 - 248, '01 - 249.

So he got roughly the exact same goal support.

The team shots against were also very equal: '00 - 1813 and '01 - 1933 (I'm not fully confident in the SA numbers due to empty nets etc., but it's very close anyway). Furthermore, Turek's own SA/G only inflated by 1 shot from '00 to '01 (again, crudely calculated) as: 22.0 SA/G in '00 and 23.1 in '01.

So my calculations have St.Louis at a win threshold of .863 in '00 and .871 in 01 (my numbers seem different than yours??)

Regardless, I only calculated this out to see if the 01 Blues were much much higher than the '00 team or if they scored much less because Turek in 01 dropped significantly from his 42 wins and .627 win% to only 24 wins and a .444 win % (with basically the same ties 9 vs 10).

Why? If a goalie's wins total is almost entirely a team based statistic, where he didn't win "because of great goaltending or because their goalie gave them clutch saves." then is it the same that Turek didn't suck the next year because of poor goaltending and untimely goals. All the team effects seem to point at a similar year for Roman.

Or is it possible that in the '00 season he played much closer to the ceiling of his capabilites and posted a .912 sv% vs McLennan's .903 .474 W% and won 42 games, and then in '01 he had a poor season personally and posted a .901 sv% vs Johnson's .907 .613W% and won only 24?

I would agree that on the Blues of those years - strong offensively and very strong defensively 20 wins were 'in the bag' but it appears that Turek and his play made a significant contribution to the other 24 win difference.

Lawrence said...

Oh, and by contrast Miikka Kiprusoff, who I choose because he won the most games last year, faced 2155 shots and 28.4/game vs Turek's best 1470 and 21.9/game.

The Blues scored 248 goals, the Flames scored 254 (only 6 more)

Kipper won 45 games (.592) with a .903 sv% over a win threshold of .897.

I guess what I am getting at is, I don't think wins, sv% and win thresholds are all relative enough to discount a goalie's effect on wins/losses, adjusted or not. I think this has a great deal to do with playing to the score, and timeliness or 'clutch' saves vs untimely goals.

I think if I gave someone not knowing the win totals of Kiprusoff, only this post and the information I used for comparison - the sv% of the two goalies, the win threshold of the two teams, and Turek's complete stats. Then, I asked you to predict Miikka Kiprusoff's win total from last year, would you deduce over 40? or even close to 45? I'm not sure I would.

Turek won 42 games (.627) with a .912 sv% over a win threshold of .867. Had Turek played 76 games, it could be estimated he would have won around 47 games...only 2, maybe 3 more than Kipper facing nearly 7 less shots/game.

Anonymous said...

Of course, the real question is why isn't Thomas Vokoun the Vesina winner, because once again Florida had terrible defence.

I've liked what Alan Ryder of hockey analytics does to calculate team defence and goalie wins, as shot quality neutral save percentage is a better measurment of how good the goalie is specifically.

The Contrarian Goaltender said...

Anonymous: I think Thomas was a deserving Vezina winner. Vokoun had a very good season as well, and you could argue that he was more valuable to his team, but I think Thomas was better in the games that he played in.

The Contrarian Goaltender said...

Lawrence: First of all, my numbers are adjusted for scoring levels, so they won't match yours exactly.

Secondly, I'm not saying goaltending has zero effect on wins. I'm saying that, in general, you can't look at win totals alone and assume anything about a goalie. Sometimes goalies can do quite a bit to win or lose games for their teams. But you need to look at all their numbers in context to be able to make that determination, you can't just say, well, he has 40 wins therefore he must have been a good goalie last year. They might have been a great team with a low win threshold that won despite mediocre goaltending.

There is certainly a difference between having a good goalie and a bad goalie. Turek in '01 was worse than Turek in '00, and therefore it wasn't surprising to see the win totals drop as well. However, Turek was never a great goalie, and he only got up to 42 wins in the first place because he played on a team with a very low win threshold.

The other issue with wins is that there is some luck from year to year. You might disagree with me that this is luck, as you might instead call it "making the timely saves". Sometimes teams win a bunch of close games and sometimes they lose a bunch of close games, so even if a goalie had an identical GAA and save percentage to the season before in the same number of games and the team had the same win threshold, it's probably that the win number would go up or down a couple of wins.

As for your Kiprusoff question, would I know the number of starts Kipper had in '08-09? Calgary's win threshold for 2008-09 was the 7th lowest in the league, so they were one of the league's best teams. The Flames were also playing in the shootout era, where wins came easier than they did before the lockout. Take those things into account, and I don't think it is surprising that Kiprusoff had 40+ wins, even with a .903 save percentage.

Anonymous said...

(I am a different Anonymous than the earlier poster.)

I have no problem at all with Thomas as Vezina winner for this year, as he was clearly the best, but I don't necessarily think Vokoun would have been a bad choice, either. (I can't imagine how Steve Mason was considered for the VT even for a moment, but I digress.)

In my opinion, Dominik Hasek in 1999 and J-S Giguere in 2003 had the two most singularly dominant regular seasons and playoffs of the decade, and perhaps the expansion era. Both completely carried teams that, besides themselves and a couple hardy role players, were very mediocre (proving their worth with a high number of shutouts, 9 for Hasek and 8 for Giggy), and both singlehandedly nearly carried their teams to the Stanley Cup--something Brodeur, Luongo, or for that matter Vokoun or Thomas haven't done. (They also won the Cup the very first year they started on a really good team.)

Why am I bringing this up? For two reasons--Nieuwendyk clearly didn't deserve the Conn in 1999 and Martin Brodeur didn't deserve the Vezina in 2003. The most immediately logical choice for Vezina based on save % in 2003 would have been Marty Turco, but after factoring in the great team effects of the uber-defensive 2003 Stars, I do think that Giguere had the greater situation-adjusted performance, and certainly carried his team much more than Turco. (Needless to say, Hasek warranted the Conn Smythe trophy in 1999.)

So, basically, I am agreeing with you that for this year Thomas was probably the best pick for the Vezina, although at the same time I can see the other Anonymous' argument for Vokoun based on the above reasoning.

seventieslord said...

This is your most interesting work yet. I'd really like to see more of this. Instead of just the top-10 and bottom-10 teams, how about which goalies had the highest and lowest weighted career win thresholds (as in, 100 games with a .910 WT team and 100 games with a .890 WT team would be a career .900)

timoseppa said...

Contrarian, that's a neat little stat. Got me thinking! Thanks.

Host PPH said...

You are right you can win even though you have the worse team. It has to do with goals.

jason bladzinski said...

I think you are preaching something that cannot be taken as real admissible proofn sports and life in general...an absolute. Obviously there is a flaw in making the statement that in life there are no absolutes, because... well making that statement is an absolute. However, let's look at your argument with that in mind. Wins may not be the ultimate factor in valuing the skill of a player, but you must realize this, the best players make their teammates around them better players. This is a part of the measure of elite teams who put together stellar seasons, that translates to wins for their team. You build a team with that goal in mind, chemistry is important, teams need to put the right players to assemble like parts in a machine. You need the right part to get the job done, and the better a GM understands this concept and has the best ability to predict the types of tools his team needs in the situations of adversity, the less adversity becomes an apparent issue. Here's the thing about goaltending in the NHL, it is the most inconsistently performed position among its players. We can see the mistakes in judgment in this when the rookie Jim Carey of the Capitals had his amazing rookie season, won a venezia, and the next season literally dropped off the face of hockey forever. I doubt you will see another rookie goaltender win the Venezia for a very long time. You see, what the league and the GM's realized is that the rarity amoung the netmiders that marked the true greats of the position is consistency. There are only a handful of goalies EVER, that were able to do what they did. That's why the wins were important, because it was so rare to find goalies who could put together 4 or more seasons of winning records despite changes in various aspects. In fact if you realize this, than you will no that those victory laden seasons for goaltenders gave them job security, the best goalies to play the game rarely played for more than 2 or 3 different clubs in their career. A goalie who played for one team his entire carreer, especially if it was a lengthy career are a testement to their greatness. No team is without change, no team no matter their length of success is without less outstanding seasonal performances. All teams see the ups and downs of the rotation of great players who come, but more importantly,go.
Back when the New Jersey Devils had an amazingly accomplished defensive style, led by future hall of fame defensemen, people called Brodeur's successes based on that. When the Devils were the best defensive team and the best offensive team as they were in their 2000 and 2001 seasons, it could be attributed that the immensive skill of their defensive game augmented by a very potent offense gave Brodeur an ever greater boost to be successful in the manner he was. Those years are gone now, and with them so too went Stevens, Neidermayer, Daneko, Rafalski, Arnott, Sykora, Guerin, Mogilany, and many others. But you know what? Brodeur had his best seasons when those guys left, and the team minus Brodeur were constantly written off because of the weaker roster, and yet even when the analyzers were against them for many years in that manner, they were putting together great seasons often finishing first or a few places lower. I say to you, Brodeur is no fraud, you are wrong, and you are jealous!
L