BOSTON -- Coach Jim Montgomery took responsibility for the Boston Bruins falling in a 2-1 series hole to the Florida Panthers after a 6-2 Game 3 loss Friday night at TD Garden.

"Our execution in the last two games has just not been good enough and that's my fault. I've got to be better," Montgomery said.

In particular, the coach accepted blame for the Bruins' sluggish start in Game 3 that saw them outshot 13-3 in the first period and 24-8 by the time the Panthers had built a 3-0 lead in the second. It was a start that quieted a raucous Boston crowd.

"We've had a couple of games where we started slow," Montgomery said. "We haven't generated much offense. I have to give the players a better plan. Florida was significantly better than us. I've got to come up with a better game plan."

The Bruins didn't show any life until the third period, when center Jakub Lauko scored to cut the deficit to 4-1 and break a streak of 10 straight Panthers goals in the series. Boston got to within 4-2, but the Florida defense and goalie Sergei Bobrovsky (15 saves) stopped the comeback.

Boston's late-game rally came after it lost captain Brad Marchand to an upper-body injury. Marchand skated eight shifts in the first period and seven in the second, amassing 10:51 in ice time before departing for good. He didn't register a shot on goal.

Montgomery said the Bruins will know more about their captain's status Saturday. But he said Marchand's absence might have served as inspiration for his players in the third period.

"I thought we rallied because of our captain," he said. "I thought our players all elevated their games and we started competing like Brad Marchand would have."

Defenseman Brandon Carlo said that winger David Pastrnak, defenseman Charlie McAvoy and winger Pat Maroon were more vocal than usual in the third period to make up for Marchand's absence.

"I think we did a good job of generating some stuff, and that's a key that they brought to the game for us," he said.

The Panthers took over with the power play. Boston rookie defenseman Mason Lohrei was whistled for a double minor for high sticking at 14:37 of the second period. Vladimir Tarasenko and Carter Verhaeghe scored on the ensuring power plays to make it 3-0.

Just 3:09 into the third period, defenseman Brandon Montour beat Jeremy Swayman (27 saves) for another power-play goal to make it 4-0. The Panthers were 4-for-6 with the man advantage.

"I think they made adjustments. They have lots of really good players. But I still have confidence in our penalty kill," said forward Jake DeBrusk, one of Boston's penalty killers. "Honestly, we've got to stay out of the [penalty] box. No matter what we think of the refs or what's going on."

But DeBrusk didn't believe the Game 3 loss fell on his coach, no matter how much blame Montgomery shouldered.

"I think that it goes both ways. We're the ones that are out there. We're the ones that are playing the game. He can put any plan that he thinks it's going to help us out, but we've got to execute," DeBrusk said. "It's about making the right one or making the right decisions and obviously we didn't do that. Against a team like that, you have to play a pretty perfect game. And the last two games you've seen what happens when we don't."

Game 4 is Sunday night in Boston.

Montgomery, who said it's back to the drawing board to find a way to knot the series, again pinned the loss on himself.

"It's too early to be able to talk about changes," he said. "We got to do our due diligence and look at the game again and see who is executing and who's playing with the effort. But it's not good enough. We didn't play well enough. That's why I take the responsibility."