Krejci's power-play goal on a one-timer set up by Charlie McAvoy at 19:59 gave the Bruins a 2-1 lead.
Reinhart tied it 2-2 at 1:43 of the third period with his sixth goal in the past four games. Victor Olofsson won a battle behind the Boston net and passed to the front for a Reinhart one-timer.
"It's always hard playing from behind, but we're a young team, we're learning, guys are getting a lot of experience," Buffalo forward Drake Caggiula said. "We believe we're in the games. There's plenty of opportunities where we could've turned this into our favor. That's sometimes the way hockey goes, but I think we can learn a lot from that."
Coyle's goal ended the longest drought of his NHL career.
"I don't go into every game saying 'Hey, I've got to score, I've got to score.' It's just about me bringing what I'm capable of bringing, what I need for the team to play well," Coyle said. "And they need a lot more than scoring goals. Is scoring goals great? Yeah, it is, and I want to do more. But that's not something that was weighing on me because then that's about me, and it's not just about me, it's about the team."
NOTES: Marchand has scored 12 points (eight goals, four assists) in the past nine games. He has scored 60 points (27 goals, 33 assists) for the sixth consecutive season, the first Bruins player to do that since Ray Bourque (13 seasons, 1981-94). … Krejci has scored five goals in the past seven games. … Pastrnak's goal was his 199th in the NHL. … Reinhart has scored 11 points (nine goals, two assists) in the past nine games. … Mittelstadt has two goals and two assists during a four-game point streak. … Boston has won six straight home games against Buffalo, which last won here Dec. 16, 2018.