In NHL, plus-minus rating can be deceiving


(Karl B. DeBlaker/Associated Press)

Anaheim’s Dustin Penner scored an even-strength goal and was on the ice for a second score during Friday’s 5-2 victory over the Calgary Flames, putting him atop the league leader board in plus-minus (plus-18). The plus−minus rating attempts to measure a player’s impact by awarding a “plus” to every player on the ice when an even-strength or short-handed goal is scored. Every player on the ice for the team scored against gets a “minus.” Unfortunately, it fails to provide a clear picture of a player’s net value on either side of the puck.

Plus-minus “is the worst stat in hockey,” Dallas Stars blue-liner Trevor Daley told the Dallas Morning News.

For example, here are two current players and the amount of shots for and against taken during even strength when they have been on the ice.

  GP TOI Shots for Shots against
Player A 25 327.2 156 213
Player B 23 327.8 142 217

Judging by these numbers it is evident that both the players and the teams around them have similar abilities in shot generation and suppression. However, both have very different plus-minus scores. Player A is Ottawa’s Jason Spezza, currently a minus-11, while Player B is James van Riemsdyk of Toronto (plus-6). The difference? The supporting cast at both ends of the ice.

Spezza is skating on a line with Milan Michalek (13 points in 26 games) and Mika Zibanejad (10 points in 18 games), who are converting 9 percent of their even-strength shots. On the defensive side, Senators goaltenders Craig Anderson and Robin Lehner have a save percentage of just 0.883 with Spezza on the ice. In Toronto, van Riemsdyk skates with Phil Kessel (23 points in 26 games) and Tyler Bozak (nine points in 14 games) while enjoying an 11.3 percent conversion rate plus a robust .959 save percentage by the netminding tandem of Johnathan Bernier and James Reimer.

In other words, having a good or bad plus-minus rating does not occur in a vacuum. Teammates can and do have a heavy influence in the metric, making it unreliable as a barometer of individual performance.

greenberg
Neil Greenberg, when he isn’t watching the games, analyzes advanced statistics in the NHL and prefers to be called a geek rather than a nerd. Follow him on Twitter: @ngreenberg.

Neil Greenberg analyzes advanced sports statistics for the Fancy Stats blog and prefers to be called a geek rather than a nerd.

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Katie Carrera · November 30, 2013