Team Level Zone Exits

From past posts, we have a general sense of the basics of zone exits: zone exits are important because they get you out of your zone and towards an opportunity to score. The key to a successful zone exit is maintaining possession, ideally by avoiding the temptation to dump the puck out.

But so far, we have only looked at zone exits league wide. Most fans care about one particular team more than the rest, but we haven’t looked at team-level results at all. So today, let’s see how each team has performed at zone exits over the past three seasons.

To start, let’s answer some basic questions. How often does each team succeed in their zone exit? And how often does each team dump the puck out rather than take a more advantageous approach?

Note that since the last post on zone exits I’ve updated my dataset to include more tracked games, so we now have almost 300,000 zone exits in data that extends to last season. Also, I’m using my measure of zone exit success, which is based on getting the next entry, not just escaping the defensive zone.

A couple of things stand out. First, we can look at the y-axis to see which teams are better or worse at zone exits: Washington, Chicago, Columbus, Carolina, and Colorado stand out for turning their zone exit attempts into zone entries almost half the time. In contrast, Ottawa, Dallas, Arizona and Florida particularly struggle.

The differences may seem small, but keep in mind that teams average 96 zone exits a game. That means that roughly 5 times a game, the Capitals create an offensive situation at a time where the Senators stay stuck playing defense.

Second, there’s clearly a relationship between dumping out the puck and overall zone exit success. The teams that dump the puck out more often tend to have worse results, and the difference is statistically significant.*

So teams are generally better off when they dump the puck out less, but is that always true? Maybe some teams have particular systems designed to succeed with more dump outs. For example, the Toronto Maple Leafs stand out here as over-performing their dump-out rate, a style which has been analyzed nicely in recent seasons. Maybe they are doing something special to ensure that they recover the puck. Let’s look at how often each team recovers their dump outs:

Indeed, the Leafs have been particularly good at recovering their dump outs, along with Edmonton, Colorado, and San Jose. In general, there’s no clear relationship between dumping the puck out more and being good at recovering it. If it’s a strategy the Leafs have adopted, there are at most two or three other teams joining them. 

So, has Toronto cracked the code on making dump outs successful? Not so fast. First, note that “better than most teams” still doesn’t mean “good”. Every team, including them, loses the puck at least 70% of the time they dump it out.

More importantly, teams may not have very much control over their recoveries at all. They can only do that if recovering dump outs is a repeatable skill. If not, no team is likely to sustain particularly good results. And it turns out that recovering dump outs is not repeatable at all.

To test this, we’ll check the repeatability of the dump out recovery rate. For each team, we’ll split their games into two groups and measure their dump out recovery rate in each one. If recovering dump outs is something that teams can control, we would expect them to perform similarly in each half. However, we see that that’s not the case:

The splits are not totally uncorrelated (R-squared of 0.17), but the relationship here is much weaker than would be expected, and it is not significantly significant. In contrast, compare this to the repeatability of how often each team dumps out the puck:

The relationship here is much tighter: R-squared value of 0.78. Teams exhibit the same zone exit decisions in both samples of games. However, once they dump out the puck, it’s literally out of their hands, and they have little ability to control what happens next.

In conclusion, teams have a meaningful variation in how often they dump out the puck. It remains unclear why: this could be a coaching decision, a natural style of the players on each roster, or the consequence of some other trait of their defensive play. But from what we can see, teams would be better served by trying to leave the zone with control of the puck more often. Any that think they are particularly good at recovering it in the neutral zone are likely fooling themselves.

What should we expect from teams next season? It is tough to estimate the impact of roster moves, but we can limit our data to last season to see the most recent results:

For player-level data, I (as always) highly recommend you support Corey Sznajder’s Patreon to get access to his spreadsheets, which will tell you the habits and success rates of each individual player. For a gif of another cool zone exit, see below:

*This is true based on a linear regression between the two variables, both with and without weighting each team by their tracked sample size. I don’t have complete confidence in applying inference here, so I welcome criticism on this point. Regardless, I think the observed relationship is meaningful regardless of direct causality.

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