The Atlanta Thrashers have two goaltenders who have essentially split duties for the last two years, Kari Lehtonen and Johan Hedberg. By every metric, Lehtonen is the better goalie of the two: they've faced roughly the same quality of shots, but Lehtonen has a better save percentage and a better goals-against-average, not just overall, but every single year.
What's even stranger is that Lehtonen consistently faces more shots than Hedberg per 60 minutes:
Where does this difference come from? It's not rebounds - they each give up approximately 9% of their shots on rebounds. So what else could it be?
It's also not that Lehtonen is somehow getting starts against better teams. This table shows the shots/60 for opposing teams, prorated to how much ice time each goalie had against each team:
So if it's not rebounds and it's not due to a better group of opponents, what is it? It's certainly not luck - while the standard deviation in shots/60 was slightly higher for the group of teams Lehtonen faced, the odds are much, much less than 0.01% that it happened by chance. It's not a home/road issue either - Lehtonen was much more likely to play at home (54%) than Hedberg (42%), so if anything this makes Lehtonen's high shot total even less likely.
So what about the impact of Atlanta players who were in the lineup when each goalie was playing? At 5-on-5 over the last two seasons (including missed shots), it's very stark:
|PCT TOI||PCT TOI||Shot/60||Shot/60|
For reasons that are unclear to me, many of Atlanta's player give up dramatically higher shot rates when Lehtonen is in goal. The top D pair of Enstrom and Havelid is particularly odd - how could they possibly give up so many more shots when Lehtonen's in goal given that the caliber of opponents is the same as when Hedberg's in goal? And it's not as though this effort (or lack thereof) is matched on the offensive end - Atlanta had 34.6 shots on goal per 60 regardless of who was in goal. A hockey mystery remains unsolved...
Some have suggested that the defensemen are aware that Hedberg is a weaker goalie and they consequently try to block more shots - that's not borne out by the stats: 12.4 blocks/game when Hedberg's in vs 12.6 for Lehtonen.
Commenter Likens has suggested that the difference in shot totals may have something to do with the score when each of these goalies are playing. Because Hedberg is demonstrably worse than Lehtonen, he ends up playing with his team behind more often. When teams are behind, they allow fewer shots, mostly because their opponents are playing more defensively.
It's true that Hedberg played behind more than Lehtonen over the last two seasons - he was down 1-3 goals 29.8% of the time versus 27.3% for Hedberg. This explains some of the difference. But what caught my eye was that when the game was tied, Lehtonen saw 47.0 shots/60, while Hedberg saw 43.3 shots/60. That's a big difference, and again, not something we can write off as luck.