Frequently Asked Question #1: A quick spin through +/- statistics at Behind the Net

by Hawerchuk on Oct 8, 2009 2:40 AM EDT in Statistics

The concept of Plus/Minus is not a new one - the Montreal Canadiens started collecting it 50 years ago, and it became an official stat when the NHL expanded to 12 teams in 1967-68. But +/- doesn't tell us everything about a player - someone who's on the ice for five goals for and five goals against gets the same +/- as someone who's on the ice for no goals. The statistical reports at Behind the Net allow you to distinguish between those two players.

After the jump - who was on the ice for the most and fewest goals, for and against, at 5-on-5 in 2008-09:

The owner of the highest positive rate is not surprising in the least, while the worst negative rate belongs to a Phoenix Coyotes player:

Highest Goals For Rate: Pavel Datsyuk +4.28/60 minutes - complete list

Highest Goals Against Rate: Enver Lisin -3.81/60 minutes - complete list

And what about +/- per 60 minutes? Michael Ryder, +2.18/60 minutes - complete list

One of the weaknesses of traditional +/- is that it tends to favor players on good teams - Bruins Ryder, Blake Wheeler, David Krejci, Phil Kessel and Marc Savard were all in the top ten in the league, which is not surprising given that Boston was the highest-scoring team at 5-on-5 in the NHL. At the same time, it penalizes players on bad teams - six New York Islanders were in the bottom 10.

We can make a small improvement on +/- by subtracting the +/- when a player is off the ice from it. That is, if a player was +1 goal per 60 minutes on the ice and his team was even when he was off, he ends up appearing the same as a guy who was even on the ice while his teammates were -1 per 60 minutes. It's not perfect, but it does make an adjustment for how good a player's teammates were. This statistic has several names - relative +/-, On-Ice/Off-Ice +/-, or simply "Rating", as I've called it on the stats page.

With this adjustment, Pavel Datsyuk still looks good, but Patrik Berglund, who had a good season on an ok team, vaults to the top. The Bruins are still there, a bit further down, while good players on bad teams, like Mark Streit, get pulled up. Complete list

The most egregious problem with this statistic shows up at the bottom of the list - the bottom four were Jay Pandolfo, Rob Niedermayer, Sammy Pahlsson and Travis Moen, who have all been sought after during their careers for their defensive ability. I'll discuss how we assess the performance of defensive forwards in a future post.

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Wow. Awesome.

Someone should make all those .ca TV talking heads pay attention to the Dion Phaneuf data, eh? I mean, listening to TSN/CBC you’d think Phaneuf was a star defenseman, an Olympic-level star.

The only hiccup in the data is that it doesn’t account for penalties taken. So Alex Semin ranks second here, but he was a HHT machine last year. He took about 20 HHTs, an awfully high number for a skill player. (And about the same number as the number of penalties he drew.)

Modern Art Notes

by TylerG on Oct 8, 2009 10:05 AM EDT reply actions

For ease of reading the stats, you have to switch to a different report to see penalties. You can find the reports under “Show Stats Report”.

http://www.behindthenet.ca/2008/new_5_on_5.php?sort=22&section=penalties&mingp=40&mintoi=10&team=&pos=

Semin took 1.5 non-coincidental penalties per 60, but drew 1.4. That differential is not vastly different from many of the other guys at the top of the list (Ryder, Savard, Ponikarovsky, Holmstrom).

by Hawerchuk on Oct 8, 2009 12:11 PM EDT up reply actions

I would point out that one of the shortcomings of the on/off-ice approach is that it doesn’t really separate your contributions from those of the players you regularly play with. I.e. if you are Pavel Datsyuk, the effect of a fourth liner like Kirk Maltby (who you rarely play with at EV) on your +/- is probably second-order at best. Meanwhile the effect of frequently having Marian Hossa on your wing is huge. The on/off-ice approach deals more with the former rather than the latter.

Of course it’s rarely the case that players play in set lines or pairings for an entire season, so you would get some ice-time differences between the Datsyuks and Hossas – which the on/off-ice method captures. However there are some exceptions (e.g. Sedin twins) in which you probably genuinely cannot separate the contributions of players from each other.

by R O on Oct 8, 2009 10:36 AM EDT reply actions

I agree. It’s very difficult to disentangle the contributions of linemates. And unlike basketball, where there are only a very small number of five-man units playing against either, a line plus a D-pair rarely get more than a handful of minutes against another line and D-pair. So you can’t regress it away like people have tried to do with the NBA.

by Hawerchuk on Oct 8, 2009 12:07 PM EDT up reply actions