Reimer, who turned 30 on Thursday, was making his first start in six games and got his third shutout of the season.
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"If that's what happens on my birthday, I'll take it every day," Reimer said. "I just tried to stay focused. You're just trying to stick to what you know, what makes you successful and keep attacking every puck the same way. I've been feeling good in practice and it turned out all right tonight."
Nick Bjugstad had a goal and an assist, Aaron Ekblad and Vincent Trocheck scored, and Evgenii Dadonov had two assists for the Panthers.
Anton Khudobin made 25 saves for Boston (44-17-8), which remained four points behind the Tampa Bay Lightning for first place in the Atlantic Division. The Bruins, who lost for the second time in nine games, lead the Toronto Maple Leafs by five points for second place in the division.
"You get these nights where offensively it's not happening and then that's when you hope you keep it out of your net," Bruins coach Bruce Cassidy said. "We've scored a lot of goals lately to win hockey games. It's probably going to come around the other way here pretty soon. We're going to need a night like they got, where we're keeping it out of our net. … You're not going to score six and eight, seven on a regular basis. Hopefully we turn around quick and start getting the goals against down to a manageable number."