How Quality of Competition Has Affected Toronto’s Corsi This Season

Over a large sample size, Corsi is one of the best measurements we have at the moment for team-level skill.  While it’s far from perfect, once you get 20 or 30 games into the season it does a pretty good job of predicting future goal scoring, and it’s a pretty stable stat, less affected by randomness than most others.  At the moment the Leafs are 12th in the NHL in score-adjusted Corsi with 52%.  In fact, they’re just .1% out of the top 10, so the Leafs are playing like a top 10 team in terms of shot attempts this season.  That suggests the Leafs have been playing well at even strength this season.

However, their results have fluctuated quite a bit over the first three months of the season.  Let’s take a look at five-game rolling average of Corsi (this chart is not score-adjusted):

While the Leafs overall number has been good, as you can see, the results have gone through two peaks and one valley.  While Toronto did a great job of out-shooting their opponents early on in the season, they went through a protracted period where they were pretty consistently getting outshot.  Then over the past 1/3 of the games they’ve played so far they’re doing fantastic (55% Corsi would be tops in the league). 

There are lots of possible explanations for the results we’re seeing here.  Maybe the Leafs made some lineup changes or shifted the ice time distribution towards less talented players.  Maybe a team with quite a few rookies is still learning to find consistency.  Maybe it’s just randomness.  In truth, it’s probably a combination of several things, but there’s one explanation that I think covers a lot of it.

Here’s Toronto’s CF% in each month of this season, as well as the average CF% of their opponents:

Toronto’s possession fell pretty drastically in November.  At the same time, the quality of their opponents rose considerably.  November saw the Leafs play five of the top six possession teams in the league (LAK, NSH, MTL, WSH, FLA) as well as #8 (CAR) and #10 (EDM).  Then the results rebounded significantly in December.  Coincidentally, the Leafs played the bottom two Corsi teams (ARI and COL) each twice in December, as well as having a game against the Canucks, who are only just barely out of the bottom five. You can see this trend quite clearly if we add the average CF% of Toronto’s opponents to the 5-game rolling average I posted above:

The trend here is unmistakable.  When the Leafs are playing average or below average teams, they perform quite well.  When they face the top teams in the league, the results are not as good.  This is exactly what I’d expect from a team in the Leafs’ position.  They’re a good team, which is why their results are solid against a majority of the league, but they’re not yet a great team, which is why they struggle against the best of the best.  In the long run I think Toronto’s overall Corsi results are a fair reflection of their talent, but in the short run a lot of things can impact results, and quality of competition is a big one.