When Corsi Analysis Goes Wrong…
Behind the Net Blog recently used even strength when game is tied Corsi analysis to take a look at the divisional imbalance since the lockout and came up with an interesting conclusion.
The NW division is slightly better than the SE division against all shared opponents. But SE division teams outshot NW teams in head-to-head games. The difference between the two divisions is negligible, though the NW’s stronger showing against the pacific and central suggests that it’s just a little bit better than the SE.
What that essentially implies is that since the lockout the northwest division is only marginally better than the southeast division, which has generally been considered the worst division in hockey since the lockout.
This though is a perfect example of where Corsi analysis fails because that statement is proven downright untrue when you consider each divisions actual won-loss records. Against the southeast division the northwest has combined for a dominating 64-31-12 and only twice has a northwest team had a losing record against the southeast (2009-10 Wild at 1-2-3 and 2008-09 Flames at 1-3-1). The 64-31-12 record is the equivalent to a 107 point team over 82 games which is awfully good. The southeasts record against the northwest is 43-49-15 which is equivalent to a 77 point team. To put that in perspective, the NW is like Phoenix (107 points) and the SE is like Columbus (79 points) this past season. That makes the northwest division more than ‘a little bit better’ than the southeast division.
In another analysis at Behind the Net blog they look at Corsi +/- for teams in games against teams in divisions other than their own. For the northeast division they came up with:
Ottawa +200, Boston +134, Toronto +65, Buffalo -60, Montreal -266.
That would seem to indicate that Toronto has been a halfway decent team but they finished last in the northwest division in 3 of the 5 seasons and never finished better than 3rd. Montreal finished ahead of the Leafs in 4 of the 5 seasons and accumulated 49 additional points in the standings despite having an outside division even strength when game is tied Corsi +/- a whopping 331 points below that of the Leafs. The Minnesota Wild had a very dismal -419 Corsi +/- outside the division but had a respectable 134-106-26 record which is equivalent to a 91 point team. Now a 91 point team is nothing special, but it is a far cry from what the 3rd worst outside division Corsi +/- would indicate their record ought to be.
In both of these posts the use of Corsi analysis has failed to accurately explain what really happened on the ice and it comes down to the fact that even strength when the game is tied Corsi numbers only tell a fraction of the story. It doesn’t account for goaltending or power play or penalty kill or shooting ability or any number of other factors that influence who wins hockey games so using it as a tool for determining which teams or divisions are better is a pointless exercise because on the ice, all those other things matter. The better tool to use in evaluating which teams or divisions are better is the much simpler and more universally understood statistic known as win-loss records. Win-loss aren’t perfect, but they don’t try to tell me that the Leafs have been better than Montreal since the lockout or that the northwest division is only marginally better than the southeast division.