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Was Boston being too aggressive on a Late Powerplay Last Night?

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The B's went full aggressiveness on the power play last night late in the 3rd with a 4 forward, one defender setup. But was it worth it?

NHL: Philadelphia Flyers at Boston Bruins Bob DeChiara-USA TODAY Sports

Using four forwards on the powerplay has become more and more popular over the years. The Bruins spend the majority of their powerplay time with four forwards, and have for a few seasons now. Powerplay units with four forwards see a boost in goal scoring. However, the other edge to this blade is that there is also a boost in goals against.

From an article at hockey-graphs.com

When Travis Konecny took a penalty with 5:30 left in the third period last night, he sent the Bruins to the powerplay with a two-goal lead. The Bruins came out with their first powerplay unit of Ryan Donato, Patrice Bergeron, Brad Marchand, David Pastrnak, and Matt Grzelcyk. Was this the optimal decision?

The quick answer is no. That is because not all goals hold equal value. If a team is up 2-0 and scores a third goal, that goal is not as valuable as a goal scored by a team down 2-0, bringing the score to 2-1. Late in the contest last night, the Bruins were almost guaranteed the win, with losing in overtime being a worst case scenario.

Expected points over time last night thanks to hockeyviz.com

This theory is referred to as leverage. Because giving up a goal would be more costly to the Bruins than the reward of scoring a goal, it would be in their best interest to deploy a unit that would better prevent a goal against. The Bruins would continue to run four forwards on the powerplay until close to the two minute mark, but should have actually stopped with nine minutes left.

If so, why did the Bruins deploy four forwards anyway?

  1. A powerplay goal in this situation still holds value. As Andy Brickley said, the Bruins were trying to put the Flyers away. Going up 3-0 late would improve the Bruins chances of winning from “extremely high” to “almost a guarantee”.
  2. The Bruins are going to continue to face a high defensive leverage situation after the powerplay is over. Giving the defensemen you plan to use to close out the game an extra breather could pay dividends.
  3. The game wasn’t out of hand and the coaching staff didn’t see the need to break up a unit that works.

In the end, these decisions aren’t as cut an dry as we’d like. There is a lot to think about, even for a seemingly small decision like this. The decision to run four forwards didn’t cost the Bruins, but they might want to think about only rolling three next time they're in situations like this