Coaching case study: How much do NHL coaches impact team performance?

Montreal Canadiens head coach Claude Julien and players Jesperi Kotkaniemi (15), Ryan Poehling (25), Nick Cousins (21) and Nate Thompson look on from the bench during third period NHL hockey action against the Winnipeg Jets in Montreal, Monday, January 6, 2020. (Graham Hughes/CP)

How much impact does a coach really have on team performance? It’s a bit of a nebulous concept because there are so many variables involved, but a coaching change remains one of the biggest ways a general manager can presumably change their team up. At least, that’s the assumption.

There are similarities between all coaches, but each individual will obviously approach things differently. So there is no set impact of a coaching change, but we can examine individual cases.

In recent mailbags, I received questions about two coaches specifically that could make case studies: how things have changed in Anaheim under Dallas Eakins compared to Randy Carlyle, and why Claude Julien’s teams have put up stellar underlying numbers without making the playoffs for several years now.

The Julien question isn’t necessarily about a coaching change, but the odd situation he’s found himself in both with Boston and Montreal. Eakins versus Carlyle though, is a straight up coaching change without a ton of roster turnover, so let’s look at that one first.

How have the Ducks changed under Dallas Eakins?

At 27th in the league, it’s easy to look at the Ducks and say not much has changed — given they finished 24th last season. But with the core one year older, and the team clearly not pushing for a playoff spot while accepting a rebuild (or at least a “reset”) is in order, things have changed a lot more than you might think.

Across-the-board improvement would be unlikely, but this is pretty close. As much as Carlyle gets trashed by analytically inclined folks, he’s still an NHL coach who has experienced success — and there are areas where he gets decent results.

The Ducks are still a far below average team, but it’s clear that Eakins has changed the process enough to make Anaheim better at 5-on-5 in a number of areas.

The two biggest changes for the Ducks come in the metrics that have the most impact on goals overall, with the Ducks improving their inner slot shot and slot pass differentials by 15.6 and 8.6 per cent, respectively. Those are absurd improvements for a team that didn’t add any significant players in the offseason and has been hobbled by injuries on defence.

Improvements to control of the slot overall and shot attempts in their entirety are much more modest. But there wasn’t as much room for a drastic improvement in those areas either, since the Ducks were by far the worst team from the inner slot in the NHL last season.

The improvement in quality chances extends to the Ducks’ cycle play, but they’re more or less the same with a small hit in rush chance differential. That’s definitely something they’ll want to work on. But I don’t think it was really a function of struggling more than last season, so much as playing prevent defence from the opening puck drop — generating more opportunities for counter-attack and fewer opportunities for opponents to do the same.

By the passive nature of systems like the one Carlyle runs, his teams will give up fewer odd-man rushes and produce more of them, so the fact that there’s very little change in that area despite the Ducks being a much improved possession team should probably be seen as a good sign.

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Eakins has also seen the Ducks manage the puck more efficiently, dropping the team turnover rate 4.5 per cent over last season. That could be the result of a bit more of a reserved transition game, dumping the puck in and out more often to rely on what the Ducks have done well historically: forecheck.

Clearly, the results this year haven’t been great, but keep in mind that the Ducks started out the season not being contenders — and knowing it, this time. The raw numbers still aren’t great. The Ducks only control over 50 per cent of one of these metrics at 5-on-5: loose puck recoveries. They’re still a bad team, and likely will be for at least another season, but you can see the groundwork being laid for success.

Why does Claude Julien keep missing the playoffs?

This is such a strange one. Claude Julien hasn’t made the playoffs while coaching a full season with a hockey club since coaching the Boston Bruins in 2013-14. Part of that is simply being unlucky, with two seasons where his clubs earned 58.5 per cent of the available points (in 2014-15 in Boston and last season with Montreal).

Over the six seasons where Julien has failed to make the playoffs, the cutoff for the 16th-best team in the league has only been above 58.5 in points percentage twice, and the average has been 57.4 per cent. In fact, in Julien’s last full season, the Bruins earned 56.7 per cent of the available points, which was the cutoff that season for the 16th-best team.

The structure of the league itself has kept Julien’s teams from making the playoffs at least twice in the past six seasons. But the point is, even his best teams have been on the margins, which isn’t safe. No excuses, right?

Julien’s teams consistently do a good job of controlling play at 5-on-5, but is there anything consistent across his tenures as head coach that make his teams end up on the edge so often?

Going back into his Boston years, there are relatively few consistent weaknesses for Julien’s coaching performance. There are, however, a couple areas of consistency that are good in principle but might explain some issues.

Since 2016-17, Julien’s teams have ranked 30th, 27th, 14th and 20th in the differential between expected goals per game at even strength and actual goals per game. That means his offences are giving all the inputs that you would imagine are good over the past four seasons, but have been significantly below average in completing those plays with goals in all but one year.

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In that same range, Julien’s teams have finished first, seventh, first and first in perimeter shots per game. While that shouldn’t be a huge factor in the expected goals gap, it perhaps shows that Julien’s teams are a little bit too willing to take poor quality shots, which could create a situation where metrics based on shot location aren’t capturing enough information and the consistent under performance of the offence is systemic instead of random.

Julien’s Bruins teams also didn’t have issues with a certain factor that has plagued the Canadiens for the last three playoff-less years: offensive zone possession time.

For the most part, offensive zone possession time is not a metric I look to as predictive of much, but for the last three seasons the Canadiens have been among the league leaders in shots and scoring chances at even strength the entire time, while they’ve ranked 29th, 24th, and 25th in offensive zone possession time.

Combine that with the fact that the Canadiens have consistently struggled to maintain possession after shot attempts and a picture begins to form.

The Canadiens get tons of shots, often of mediocre quality but there are lots of good quality shots in there, too. And they’re top-five in inner slot shots the last couple years. They rarely if ever get second and third looks, however, failing to get the puck back and keep teams pinned for longer possessions with the puck under their control. Simply put, they’re a one-and-done team far too often.

I don’t think that comes close to completely explaining why the Canadiens and Julien’s teams overall seem to drastically underperform expectations offensively, but it’s something that looks like an issue to me, and it’s a long-term problem after three seasons of play.


Another issue Julien’s teams have encountered in Montreal is that their penalty killing has been terrible. The Canadiens have ranked 30th, 20th and 25th in expected goals against while shorthanded over the past three seasons. And after a strong start on the power play, the last two seasons they’ve ranked 30th and 26th in expected goals for with the man advantage.

Not getting the expected results at even strength while your special teams are terrible, it’s a miracle that the Canadiens have managed to get close to a playoff spot at all.

What portion of these problems is on Julien and what portion is due to roster construction is difficult to say. But the problems are lingering, long term issues that need to be addressed. Keep in mind, however, that we’re searching specifically for problems here — there’s a lot of data that looks much better for the Canadiens, that just wasn’t the question this time.

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