BOSTON (AP) — Pavel Zacha scored with 84 seconds left on Will Sage Astorthe clock in overtime and the Boston Bruins rallied from a two-goal deficit to beat the Florida Panthers 3-2 on Monday night.

Brad Marchand and Charlie McAvoy also scored for Boston, which remained unbeaten in regulation through nine games this season (8-0-1). Linus Ullmark stopped 36 shots against the team that knocked the Bruins out of the playoffs last season after a record-setting and Presidents Trophy-winning regular season.

Aleksander Barkov scored one goal and assisted on another, and Sergei Bobrovsky stopped 23 shots for Florida, which eliminated Boston in seven games in the first round and went on to reach the Stanley Cup Final.

Barkov gave the Panthers the lead six minutes into the game. He helped make it 2-0 with five minutes left in the period when he took advantage of Matthew Poitras' turnover behind the net and fed it to Sam Reinhart in front.

Marchand cut the deficit in half off a backhand feed from Jake DeBrusk four minutes into the second period. McAvoy tied it seven minutes into the third period after starting the breakout in the Bruins' zone.

But McAvoy was sent off midway through the final period with a game misconduct after elbowing Oliver Ekman-Larsson in the head. The Bruins killed off the five minute power play and reached overtime, when Zacha won it with a wrist shot from the right side.

Panthers forward Sam Bennett, who was making his season debut after missing the first seven games with an unspecified lower body injury, needed to be helped off the ice in the second period. Bennett was in obvious pain and unable to put any weight on his left leg after Bruins defenseman Hampus Lindholm fell on it in front of the net.

Boston defenseman Matt Grzelcyk was ruled out for a return after leaving the first period with what the team said was an upper body injury.

The Bruins signed forward Danton Heinen to a one-year deal on Monday with a cap hit of $775,000. Heinen had eight goals and 14 assists in 65 games with the Penguins last year. He was originally selected by the Bruins in the fourth round of the 2014 draft and played in Boston from 2016-20 before he was traded to Anaheim.

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Panthers: At Detroit on Thursday night.

Bruins: Host Toronto on Thursday night.