Down, 1-0, to the Rangers after 20 minutes, despite an at-times dominating first period by the Bruins, it was the top line that jumpstarted things on the scoresheet with a brilliant opening shift to start the second that included two goals in 57 seconds to put Boston ahead for good.
The first came just 11 seconds into the middle frame when Pastrnak drove to the net after collecting a feed from Marchand off the opening draw. The winger charged to the net and was tripped by diving New York defenseman Libor Hajek, causing Pastrnak to barrel into Rangers goalie Henrik Lundqvist.
With Lundqvist down in the crease, Bergeron swooped in to lift home a backhander that knotted the game at 1. The goal was reviewed, but it was determined that the Rangers initiated the collision negating any goaltender interference.
"They generate a break, they went to the net and got it," said Cassidy, whose team outshot the Rangers, 21-5, in the second period. "At the end of the day, we felt we outplayed them in the first period and if we just stuck to what we do well and what we were doing we'd be OK.
"Ran a nice face-off play to start the second period and got rewarded. Some of those calls have not gone our way this year. That one, the goal stood, and we were pretty good after that."
Indeed, they were. Including Bergeron's tally, Boston scored five straight goals - two from Marchand and one each from Charlie Coyle and Zdeno Chara, whose blast from the point just 43 seconds into the third proved to be the winner.
But it was Marchand's goal only 57 seconds after Bergeron's opening marker that was by far the prettiest. The 31-year-old took Pastrnak's feed at the top of the crease and dangled around Lundqvist - while standing still - with a filthy backhander to put the Bruins up, 2-1, at 1:08 of the second.
"Stay with it. We've been there before. You're a shot away, we've had some good looks. I thought it was a good period," Bergeron said of the message after the first. "Couple plays here and there that could've been better, but still I think we were having a pretty good period. Obviously getting the two quick goals to start the second got us going."