The Puck Stops Here

Whenever we do sabermetrics it is important to ask ourselves if the results we get make sense. It is important to check to make sure that we are not getting unintended results because of circumstances we did not properly take into consideration.

Recently, I have written about the adjusting scoring from different eras to do player comparisons using a method devised by the hockey outsider (Peter Albert). The top 10 single season adjusted goal scoring list produced by this method lists Brett Hull's 1990/91 86 goal season with the St Louis Blues as the best goal scoring season ever. Is this result accurate?

Brett Hull played 78 games that season. He scored 86 goals, 45 assists for 131 points and won the Hart Trophy as NHL MVP. His lead in the goal scoring department was dramatic. In second place was a three way tie between Theo Fleury of Calgary, Cam Neely of Boston and Steve Yzerman of Detroit who each scored 51 goals. Hull scored 68.6% more goals than his closest opponent. Hull finished second in scoring in the NHL that season, finishing behind Wayne Gretzky of the Los Angeles Kings, who had 163 points (due to a staggering 122 assists). Brett Hull was teamed with Adam Oates who was his setup man. Oates finished second in assists behind Gretzky. In Hull's career which ended last season, he never again managed as many goals in a season, though it may be partly because he never had a full season with Adam Oates as his centreman. Oates was traded to Boston midway through the next season.

Brett Hull came within 6 goals of breaking Wayne Gretzky's single season record of 92 goals and he did in in a time when scoring had dropped from when Gretzky set the record. Nobody has scored as many goals in a season as Hull did that season in any year since. This is partly because scoring has dropped leaguewide since that time. Most shockingly, Hull did not have this season in an expansion weakened NHL - since quality of opposition is not taken into account in this statistics adjustment players in weaker NHL seasons tend to dominate. There had been no NHL expansion since 1979 and the next expansion (the San Jose Sharks) happened the following season. Hull leads the top ten adjusted scoring goal scoring single season list by a full five goals over Phil Esposito's 1970/71 season (which was an expansion year). This is a 7% increase over Esposito's adjusted goal scoring numbers, which is probably large enough to be significant (when considering the fact that Esposito played in an expansion weakened NHL). I think the pick of Brett Hull's 1990/91 season as the best goal scoring year ever is a good one.

Now does this mean Brett Hull is the best goal scorer ever? No. One year doesn't make a career. Also, goal scoring is not a solo act. Most great goal scoring seasons occurred because there was a very successful linemate who was setting up the goal scorer. In Hull's case Adam Oates filled that role. It is not an easy problem to separate how much of the credit should go to Hull and how much should go to Oates (or other teammates). This is one of the problems in hockey sabermetrics. Player's contributions interact in complicated ways. When players have good "chemistry" both of their statistics are improved. When a player plays equally well without the "chemistry" with a linemate his numbers are not as good. This is true of his linemate as well. How much credit goes to either player so that he would hold the same value with or without his all star linemate is an unsolved problem. Ideally, a player should have the same value to his team regardless of who his linemates are. Otherwise, his "value" is not truly due to his contribution. It is unsatisfactory to compare players with one another when the value of the player is due to his teammates and not the player in question. Can this problem be solved? I don't think hockey collects enough statistics to do so (I would love to be proven wrong). I don't know which other statistics are needed. We need to know more about the circumstances of when a player gives and receives passes from his teammates for example. Right now we can compare (for example) the best goal scoring seasons, but we cannot compare the best seasons. We know when circumstances came together that somebody had a top goal scoring season, but that doesn't show that how much of that season was due to the player who scored the goals and how much came from teammates setting them up. Clearly, to have the best goal scoring season ever, one must be a very good goal scorer, but it is not necessary to be the best goal scorer ever. A top setup man like Adam Oates might make up the difference between Hull's season and (for example) Mario Lemieux's 1988/89 season where he scored 85 goals (75 adjusted goals) but did not have a player as good as Adam Oates to feed him the puck. In fact, Lemieux was also the best assist man in the NHL that season. Teammates Paul Coffey (on defence) and Rob Brown were the forth and sixth place finishers respectively in assists. It is widely believed that Brown's success was due to being Lemieux's linemate and Coffey and Lemieux often appeared on the ice separately (though not so often during power plays). So do we would Lemieux's season have a better goal scoring value when decoupled from teammates? Quite possibly, but we lack a reliable method to do this.

Brett Hull's 1990/91 season was a very good year. It was the best goal scoring season in the history of hockey. I think the sabermetrics are accurate. How much of this credit should go to Hull and how much to teammates (specifically Adam Oates) is unclear. It is entirely possible that Hull's season while it was the best (adjusted) goal scoring season ever, it was not the best goal scoring season that can be credited to one player ever. Decoupling the contribution of teammates to a combined success is an unsolved sabermetric problem.