How are the Bruins without the Bergeron line?

Data via Corsica, visualizations from HockeyViz.com

The Bruins will face off against the Carolina Hurricanes tomorrow night for their last game in October. The Bruins are 6-3-2 after a horrific opening game against the Capitals. Their goal differential of +7 is far better than Buffalo, who have accrued one less point in the same number of games. There are a lot of positives in Boston, but as I browse through my Twitter feed, I see a whole different attitude.

Going into the season, the Bruins knew their depth was a problem. It’s been a problem for years now. The Bruins top line is the most dominant line in the NHL, and the Bruins are not going to be as strong without them. But how much worse are the Bruins without them on the ice, and where do the problems exist?

Let’s try to pinpoint the problem.

Offense:

We’ll start out with looking at the Bruins offense with and without the Bergeron line on the ice this season. Just looking at individual goals scored at 5v5, the majority of Bruins goals have come from Brad Marchand, Patrice Bergeron, and David Pastrnak this season.

But scoring goals is only part of the equation. You can’t keep scoring goals if you are not getting many opportunities to score. But the Bergeron line is doing that a lot better than their teammates. When the Bergeron line is on the ice, they take 50.8 unblocked shot attempts per hour. When they are not on the ice, that number drops to 38.2.

As you can see from the chart above, the Bergeron line not only produces a lot more shot attempts, but produces quality ones. The Bruins see a 0.72 increase in their expected goals per hour, and a 2.49 jump in their goals scored per hour.

The Bergeron line is currently shooting a little more than 3% above their expected shooting percentage so far this season. While they will probably continue to sustain a higher shooting percentage than expected due to their shooting skill and pre-shot movement, they won’t be able to outperform it by the margin we see now, so their 4.3 goals per hour will eventually fall.

Meanwhile the Bruins are shooting under their shooting percentage, just slightly, at 0.44%. And while we expect to see that rise, unless the Bruins start producing more shot attempts per hour without the Bergeron line on the ice, there will still be a large gap in goal scoring.

Defense:

On the other side of the puck, the Bruins hold their ground without the Bergeron line on the ice. The Bruins still perform better defensively with the Bergeron line on the ice, but the gap is a lot closer.

The Bruins give up 1.1 less unblocked shot attempts per hour with the Bergeron line on the ice. Combining that with shot quality, the Bruins expect to give up 0.14 less goals per hour with the Bergeron line on the ice.

Something that I haven’t seen pointed out is that the Bruins save percentage drops 7% with the Bergeron line on the ice. So far this season, the Bruins have given up 2.1 more goals per hour with the Bergeron line on the ice. This is not their fault, and that will regress.

Conclusions and notes:

The Bruins are able to hold their own while the Bergeron line is not on the ice. They practically break even with teams without the Bergeron line, allowing their top line to tilt the ice.

This is what we have seen over the last couple of years. Whether it’s purposeful or not, the Bruins play a dull game without the top line on the ice.

By minimizing the events that occur, the Bruins decrease the variance in possible outcomes. This allows their top line, which plays at a higher pace, to win games through dominating their opponents.