But they also saw the Maple Leafs wrench back momentum, beginning with a highlight-reel forehand-to-backhand goal by Zach Hyman at 16:52 on which he outskated and outpowered Krejci and defenseman Charlie McAvoy. Toronto got the upper hand for a while but could not sustain it, even through two early power plays in the second period.
"They made a push but, again, [it was a] good character response to be able to get back to our game, get back to our principles," Backes said.
The Bruins took back the lead with a Backes power-play goal at 15:43 of the second, extended it with a David Pastrnak dagger with 38 seconds remaining in the period. And then, at least for the Maple Leafs, it turned ugly. Sean Kuraly batted the puck out of the air for a goal at 7:41 of the third, and there was yet another power-play goal, by Krejci, at 11:29.
The Bruins had taken a four-goal lead and command and had shown a generally young Maple Leafs team exactly who they are and have been for most of the season.
"To me, when you get beat you just sort of regroup," Toronto coach Mike Babcock said. "We have a day to solve our problems and we can feel sorry for ourselves here tonight, but that's a waste of time and energy."
The Maple Leafs will need to regroup by Saturday, for Game 2 at TD Garden (8 p.m. ET; NBC, CBC, TVAS). They will need to find a way forward. Because the Bruins were the better team Thursday, no question. They weren't distracted. They weren't pondering what could have been, had they won any of those four games.
They were laser focused. They were ready.