BOSTON — Bruce Cassidy showed on several occasions throughout the regular season that he was not afraid to tinker with his lines mid-game when he did not like what he was seeing from his team.

The Bruins struggled to muster much in terms of actual scoring chances while at even strength in a 4-1 Game 1 loss to the Toronto Maple Leafs on Thursday at TD Garden.

Boston’s elite top-line trio of Patrice Bergeron, Brad Marchand and David Pastrnak were held pointless on 5-on-5 thanks to the defensive work of Nakita Zaitsev and Jake Muzzin on the Leafs’ back end.

But Cassidy stuck with his forward lines for much of the game, save for a stint in the second period when Jake DeBrusk left the game with a minor injury (he’s fine, by the way).

When asked why he decided not to change things up, Cassidy took a long, long pause.

“You know, we lost Jake for a little bit, so that effected us a little in the second, so we moved (Pastrnak) around a little with (Charlie Coyle),” Cassidy finally noted. “But we’re trying to get that top line going. We’re still in the game. Regular season is a little different than playoffs. You’re trying to stick with it. So that’s probably the biggest reason.

“Some of the guys that usually move around, listen, I didn’t love their game,” Cassidy added. “So when they are on, I’ll move them around, double shift them. Couple of the guys that that’s happened to in the past, I didn’t know if it would’ve helped them to be honest with you.”

The most notable change Cassidy usually turns to, and a look the Bruins rolled with toward the end of the regular season was shifting Pastrnak down to David Krejci’s flank on the second line opposite DeBrusk. That usually would, in turn, shift Danton Heinen up to the first line.

But Heinen stayed put on the third line, which arguably was Boston’s best line offensively at even strength Thursday night, firing off nine shots. Coyle followed that effort up with a game-high seven hits. Karson Kuhlman logged the entire game on the second line, putting up three shots in 13:34 time on ice.

And you can’t fault Cassidy too much for being hesitant to break up that potent top line, which torched the Leafs in last year’s first-round series.

“Some of that in season, too, is to get their attention, reward other guys,” Cassidy added. “We’re now in the playoffs. Right? There shouldn’t be attention-getting. It’s about ‘hey, let’s get out there and be better than the guy across from you.'”

If the Bruins come out in Game 2 as they did in Game 1, it will be worth monitoring if Cassidy decides to then get some players’ attention with changes.

Thumbnail photo via Bob DeChiara/USA TODAY Sports Images