Earlier this month, the Islanders traded for and then signed Jaroslav Halak. It’s not surprising that the Islanders traded for a new goaltender, as the Islanders were last in the league last season in terms of team save percentage.
A few weeks back, I unveiled Hockey Marcels: an extremely simplistic system for projecting goalies performance going forward, utilizing just the last four years of a goalies’ play to do so. Building off of work by the great Eric T., I weighted more recent years more heavily than older ones, to try and give a better estimation to what we should expect from goalies going forward. In addition, I added a regression factor to Eric’s work, such that we could deal with varying sample sizes and the extreme variability of NHL goaltending.
But the one thing I didn’t include was an aging adjustment. This is an integral part of any serious projection system for the obvious reason: Using past years to project future data is sound, but players will be OLDER in the future and increased age generally results in worse performance (except for the really young). This is especially the case with hockey, where peak performance has been found to be at ages 24-25. If we really want to project goalie performance going forward, we need to find out how well goalies age.
A few people have looked at this before (both Eric and Steve Burtch have written about goalie aging in previous posts), but I wanted to actually get #s rather than just a graph on how aging affects goalies of all ages. So I used hockey reference to get the seasonal data of all goalies from 1996-1997 to the present season who had played 20 years, and tried to take a look.
Due to starting my dive into hockey statistics as a Winnipeg Jets fan, save percentage has always been a pretty big interest of mine, specifically in what it can and can’t tell us. The truth is, it is still a pretty rudimentary statistic and likely will be improved upon in the future. However, simple does not always mean bad or useless.
Of the three most common “goaltender statistics”, save percentage is the one controlled most by goaltenders. How can I be so sure of that? Well it can be provided with simple logic.