BOSTON -- The Buffalo Sabres had every reason to pack it in trailing by three goals midway through Saturday night's game against the Boston Bruins.

After all, the Sabres were 1-5-2 on the young season and playing the back end of a back-to-back -- after losing at home to the Vancouver Canucks Friday night.

But they didn't quit.

"I think we need to use this game as an example of what it takes to win a hockey game," Jack Eichel said after his team roared back, tied the game with 2:08 left in regulation and won it 5-4 on Ryan O'Reilly's goal at 2:59 of overtime.

O'Reilly, who had an earlier assist, picked up a shot from Risto Ristolainen that went wide, did a spin from behind the net, moved out front and backhanded the winner past Anton Khudobin for his fourth goal of the season. The Bruins challenged after Evander Kane fell on Khudobin, but the replay showed Boston's Torey Krug had pushed Kane into the goaltender.

"It wasn't a great backhand, I just kind of raised it and it sneaked in," O'Reilly said. "It was a nice bounce for us, we haven't had a lot of those lately. Again, we're going to start preparing for the next game. We're still disappointed with our start in the season and we've got to get better."

As far as having to wait to make sure the goal stood, O'Reilly said, "I was just getting right to the bench. It was out of our hands at that point, and I was just getting ready, getting my rest in case we had another shift and to leave it all out there. Because you never know.

"You never know with those situations. You know, it was a good bounce (off the boards). You could tell all the guys, we needed a break like that after kind of dominating OT. It was nice. It was nice to get that bounce."

David Pastrnak and Brad Marchand scored two goals apiece as the Bruins (3-3-1) built their lead. Pastrnak's second goal of the game and sixth of the season established the three-goal lead 11:22 into the second period, but Eichel, the former Boston University star who had a large contingent of family and friends on hand, scored on a rebound later in the period.

The Sabres poured the pressure on in the third and Benoit Pouliot's first goal with his new team made it 4-3 before Kane tied it with a backhander that slid in off Krug's skate with 2:08 left in regulation.

After totaling 15 shots in the third period, the Sabres outshot the Bruins 6-0 in overtime with their 21 shots in the final 22:59 matching their first 40 minutes.

"I give our guys a lot of credit because they've been through a lot in just a short period of time, and, on a back-to-back night," said coach Phil Housley, who has two wins as a head coach.

Marchand scored his fifth and sixth goals of the season and has five goals and five assists during a five-game point streak.

"As it went along you could see that ... it's hard to reel it back in for whatever reason," said Bruins coach Bruce Cassidy. "Some of it is maybe guys aren't used to being in that position, some of it could have been the other team's just putting a lot of pressure on you because they're good and they want to win -- we weren't able to temper it.

"I think they wanted the puck more than we did."

Defenseman Charlie McAvoy, who also played at BU, had two assists for the Bruins, while Jason Pominville scored the other Buffalo goal and set up the tying tally for his ninth point in the last seven games.

Robin Lehner made 27 saves in his first win in five starts this season -- the victory raising his career record against the Bruins to 4-10-3.

Khudobin, against starting for Tuukka Rask, made 37 saves but fell to 2-1.

"It's even more disappointing when you're winning like this and you lose," Khudobin said. "This is much more disappointing than a regular loss."

The Bruins swept the Sabres in last year's season series for the first time -- going 4-0-0 and outscoring Buffalo 13-4.

NOTES: Bruins C David Krejci, who left Thursday night's Boston win with an upper-body injury, skated in warmups but did not play. ... After losing D Adam McQuaid to a broken leg, Boston was also without D Kevan Miller, who arrived at TD Garden with his hand in a cast. To replace the pair, D Paul Postma made his Bruins debut and D Rob O'Gara was recalled on an emergency basis for his first game of the season. ... The Sabres, hit hard with injuries on the defense, added Nathan Beaulieu to the list after he suffered an upper-body injury Friday night. ... Boston C Riley Nash picked up his 100th NHL point.