I got linked recently from the CalgaryPuck forum, where they are debating whether Kiprusoff's poor numbers this season were because of him being overworked. One of the posters did a nice little study that suggests games played has little impact on the numbers, by comparing save percentages before, during, and after either a 2-season or a 3-season stretch of playing 68 or more games. There was very little difference in the results (save percentages before and after were all +/- .004 from how the goalies did in their high-workload seasons).
One criticism of this technique, however, is that even if goalie fatigue is generally overrated, Miikka Kiprusoff might still be a unique case with a specific weakness in that area. I decided to look at Kiprusoff's results to see if they can tell us anything about his workload:
I pulled the game logs for each of Kipper's last 5 seasons, and looked at the number of days between starts. Here are the overall results:
1: 2.98 GAA, .897 sv%, .565 win %
2: 2.43 GAA, .914 sv%, .626 win %
3: 2.33 GAA, .919 sv%, .636 win %
4: 2.05 GAA, .930 sv%, .635 win %
5+: 2.36 GAA, .915 sv%, .769 win %
Kiprusoff did not do very well in back-to-back starts, but performing poorly in back-to-backs is not unique to him. Teams generally do worse, so part of that is likely to be the rest of the team. If Kiprusoff got at least one day of rest between games, then he played pretty well, and he (and his teammates) did slightly better with additional rest.
Looking at the 2008-09 results, Kiprusoff played 9 back-to-back games, which is the most he played in any single season. His results: 2-7-0, 3.23, .899, suggesting that he was overworked by his coach.
I disagree, however. I think there are two reasons why this is not valid as an excuse for Kipper's overall poor play:
1. Kiprusoff did not do substantially better with 1, 2, or 3 days rest in 2008-09.
1 day rest: 24-11-2, 2.83, .904
2 days rest: 11-6-0, 2.80, .907
3 days rest: 4-2-0, 3.37, .899
2. Calgary as a team obviously played poorly in back-to-back games.
Kiprusoff faced 2.5 extra shots against in his back-to-back starts. That explains why he allowed 0.4 more goals per game with a .005 drop in save percentage. He also had a much worse record, indicating that the rest of the team didn't score much in front of him.
It would have helped Kiprusoff's stats if he didn't play in those back-to-back games. It probably wouldn't have helped the team much, though. The only difference would have been that it would have been Curtis McElhinney getting shelled instead of Kipper. Kiprusoff doesn't have a pattern of strong performance in back-to-back games, but a lot of this appears to be the effect of travel for a West Coast team like Calgary.
If we take out the back-to-backs, it is still apparent that Kipper's best days are behind him. I looked at his numbers for games with between 1 and 3 days rest over the last several seasons, to get a better comparison:
2008-09: 39-19-2, 2.88, .904
2007-08: 33-23-10, 2.61, .908
2006-07: 35-22-7, 2.45, .918
2005-06: 35-16-8, 1.90, .929
2003-04: 20-9-3, 1.61, .938
Unless there is some cumulative wear effect, it's not his seasonal workload that is the cause for Kiprusoff's poor play. He is simply getting worse.
We see the decline even when we break it down further by the number of days rest between games. Here are the seasonal save percentages from 2003-04 to 2008-09:
0 days rest: .929, .889, .901, .893, .899
1 day rest: .940, .928, .906, .907, .904
2 days rest: .927, .928, .931, .903, .907
3+ days rest: .917, .938, .946, .922, .905
To me, the numbers in the last two columns don't suggest an overworked goalie, just a mediocre one. The only year where it really looks like rest was a big help for Kiprusoff was 2006-07. I'd still bet that a lot of that was randomness, however, since the seasonal sample sizes here are pretty small.
An interesting study would be to look at shot quality results for goalies playing in back-to-back games, to see if we can better break down the responsibility of the dropoff between the goalie and the defence. Until then, I think it is likely that the blame is split between both parties, but we can't go much further than that.
Kiprusoff's numbers might have benefitted if Keenan spelled him a few times when the Flames were playing on consecutive nights, as Calgary seems to have played poorly as a team in back-to-backs this year. That does not come close to explaining his regression this year or last year. Kiprusoff hasn't been an elite goalie since 2007, and right now he's probably not even an average goalie, gaudy win totals notwithstanding. If workload has anything at all do with his results, it is far more likely to be the cumulative effects of playing a 70+ game workload for 4 years in a row rather than anything specifically related to 2008-09.