I have always believed that goaltending is by far the most important position in hockey and have claimed it can make or break any teams season. I have claimed that the main reason that the Leafs have failed to make the playoffs post lockout is because of bad goaltending. Many others have scoffed at this claim blaming everything from bad defense to bad offense (which is mostly not factually true) to poor coaching, to a combination of all of the above. I have seen others claim that goaltending would account for at most four or five games a year. So, I have undertaken a bit of a study to attempt to figure out how important goaltending really is and how many points in the standings poor goaltending can cost you or great goaltending can gain you.
Most goaltending studies I have seen, and done myself, have to do with comparing goalies from one team to the next. The problem with this is people can easily choose to dismiss the study with claims like ‘but team x has such a bad defense you cannot blame the goalie for that’ and to some extent there is some validity in this claim (though I do not believe it to be as much as many do). There have been other studies that attempt to factor out the defense issue by coming up with some sort of shot difficulty rating based on shot type and defense. I believe that this has some merit and improves the validity of the study but people will simply jump in and claim that not all shots from the same distance are equal and teams with bad defense will inherently give up more difficult shots so the shot quality analysis is still far from perfect. Again, there is some merit to this.
So, with all that in mind I set out to study goaltending in a way that eliminates the quality of a team’s defense in a way that most sane people cannot dispute: compare goalies who play on the same team. If we are comparing two goalies who play on the same team we immediately eliminate the ‘but he plays on a bad team’ argument because they are playing behind the same players.
I collected all the goalie statistics from the 5 regular seasons since the NHL lockout of the 2004-05 season. For each team and season I identified each team’s starting goalie (the goalie with the most starts) and then grouped all other goalies who played for that team in that season and merged their statistics into a combined backup goalie statistic. For example, this past season Jonas Hiller was the starter for the Anaheim Ducks and JS Giguere and Curtis McElhinney also played for the Ducks so Giguere and McElhinney’s stats were combined into a single team backup stat. The statistics I am interested in are save percentage and points earned for their team and the number of games started from which we can calculate points earned per start stat for the starter and the combined backup. I next subtracted the backups points per start from the starters points per start and the backups save percentage from the starters save percentage. Here is an example for the Anaheim goalies.
So, from that table we see that Jonas Hiller had a save percentage 0.0618 higher than his backups and produced more points for his team in the standings at a rate of 0.0128 per start. Now since that last stat is pretty meaningless I prorated it to 82 games and over the course of 82 games Hiller would produce 5.07 additional points in the standings over his backups.