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Seemingly every season there comes a time when the old debate raises its head, with some pundit questioning the validity of the new metrics like Corsi and Fenwick. They argue that possession does very little to win a game if you don’t ever score, and the analysts fire back that a single game is too small a sample size to be significant. Unfortunately, the fans are caught in the middle, not knowing who to trust.

The pundits are right.

Even strength Corsi, for example, is pretty awful in determining the outcome a single game, especially if you’re trying to compare it to points in the standings.

Part of the problem is how the NHL’s current point system rewards teams for getting to overtime, much less a shootout. Both of those game states (OT, shootout) are far more likely to be decided by a lucky bounce than typical 5-on-5 play, which means it’s not unusual for dominant teams to lose.

But we can remove some randomness from a team’s win-loss record. By breaking out exactly which were regulation wins and losses instead of OT or shootout wins and losses, we get a clearer picture of how we think games should go based on the team’s play. I call this Weighted Win-Loss Record (Wt. W/L for short).

Looking at Corsi For percentage against Wt. W/L on a game-by-game basis (three randomly chosen teams, full seasons worth of games), you can see there’s very little correlation between the two.

While last season showed a little more correlation, it’s still nothing to write home about. However, there is one stat that matches up quite well on a game-by-game basis.

PDO is a stat that adds up a team’s shooting percentage and save percentage. Given the often “random” nature of goals, it’s frequently considered a measure of puck luck, at least on a single game basis like this.

Given that luck is what seems to be the biggest factor in a single game, it’s no surprise that Corsi is so easily dismissed.

But not only do the pundits have a point – Corsi isn’t a great predictor of who will win a single game – the analysts are correct too.

Over a long enough period of time, say, 82 games, possession does indicate who will do better in the standings.

While this year was slightly less predictable than last, the correlation (often depicted by the R² value shown, where 1.0 is the best possible rating) over the season is much higher than for the single games.

And, it’s actually better than PDO.

So while yes, in a single game, anything can happen – you can get the flukey goal like the one Antoine Roussel scored Saturday night – some of the old clichés are proven out by advanced stats.

Good teams play well every night, and are rewarded in the standings.

However, we can take it one step further to really cement our understanding of how the standings ended up the way they did. After all, while PDO’s signal is weakened over the course of a season, there’s no denying that some teams (like the New York Rangers) have banked some wins on the strength of PDO alone.

Now, to be clear, the “expectations” are set by what we’ve seen from the play over the course of a season, not where anyone predicted a team to finish. So while the Rangers did have an unsustainable run of excellent PDO this season, you would expect them to pick up points off the strength of Lundqvist’s early performance. And they did.

Meanwhile, last year Ottawa got lucky and picked up enough points to join the group of playoff bound teams (in red). While luck is fleeting and they were eliminated in the first round, the points equaled observed performance.

On the other hand, both Vancouver and Calgary’s points well exceeded the play you saw during last season, even when factoring in lucky bounces. Hence, most analysts felt quite smug when both teams were bounced from the postseason.

Probably most interestingly, you can see the year-over-year change in the teams who tanked last season. Buffalo and Arizona still had bad seasons this year, but now are actually within a “normal” range of bad (a single deviation ends at negative one).

Edmonton, on the other hand, continues to languish on the outside of the pack, suggesting their problems in play still haven’t been remedied, even by wunderkind Connor McDavid.

And all of this matches up with what is considered to be the “eye-test”. It makes sense that this is how the standings turn out just from what can be observed during the games.

No, not every game will be won by the team with the best possession, but the teams with good possession will win more games. And that’s why, despite luck, despite randomness, Corsi, is just as important as the events our eyes are good at recognizing, like goals.