The Pronger Effect: How much impact can one player have?

Eric T.
May 17 2012 07:36AM

One of the most eye-popping things I have seen in non-traditional statistics was the difference between how the Flyers performed last year with Chris Pronger and without him. The plot below shows what fraction of the shot attempts the Flyers got (their Corsi score), which correlates extremely well with puck possession, zone time, and scoring chances.

Flyers Corsi drops dramatically with Pronger out of the lineup

When Pronger was in the lineup, the Flyers were getting 53.2% of the chances -- a typical number for a top-tier team. When he was out of the lineup, they were below average, a trend that continued into this season.

Certainly, Pronger is an important player, but could one player really make that big of a difference? It seemed impossible -- the difference between being a 48% Corsi team and a 53% Corsi team is huge. Teams in the neighborhood of 53% Corsi this year included the Red Wings, Kings, Blackhawks, and Bruins; teams in the neighborhood of 48% included the Hurricanes, Ducks, Sabres, Oilers, and Blue Jackets.

I don't believe that if the Blue Jackets added Pronger they would suddenly be a championship contender, so simple variance had to be playing a role here -- over a small sample size, random chance gives you some results that are more extreme than what the true effect will show in the long run.

But how big is the effect really? To answer that, I started making a list of very good players who missed somewhere between 20 and 60 games in a season recently, giving us a sample of at least 20 games with them in the lineup and at least 20 with them out of the lineup. For each of those players, I pulled the team's Corsi score with and without the player in the lineup. To eliminate score effects (the tendency of teams to go into a defensive shell to protect a lead), I used Corsi close, which only counts the shots when the score is within one goal in the first two periods or tied in the third.

Here's what I found:

Impact of top players on team Corsi

Obviously this is not a comprehensive list of injuries; I was just skimming through a list of games played and looking for the names that popped out at me as being important players.

Still, the trend seems clear: there is some variance over a ~20-40 game span and Pronger's impact probably was indeed overstated, but adding a top-tier player to the lineup does seem to result in a roughly 2% boost to a team's Corsi score -- roughly the difference between the Sharks and the Avalanche or between the Capitals and the Canadiens.

An elite talent may not be an absolute necessity in hockey the way it is in basketball, but the upper-tier players still have a big impact on the team's results.

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Eric T. writes for NHL Numbers and Broad Street Hockey. His work generally focuses on analytical investigations and covers all phases of the game. You can find him on Twitter as @BSH_EricT.