BOSTON -- Patrice Bergeron and a few of his teammates were certain the game was over, even staying on the ice ready to celebrate for a second time while his goal was being reviewed.
"I thought for sure it was in, especially after that second kick at it," Bergeron said. "Marshy (Brad Marchand) was standing right there. He said it was definitely in after the second time."
Bergeron deflected a shot from the left circle that broke off Ottawa goalie Robin Lehner and trickled across the goal line. The crowd roared, the light went on and horn sounded, but the referee behind the net waved it off.
Bergeron, Marchand and defenseman Andrew Ference -- three of Boston's four skaters on the ice -- celebrated in front of the Senators' net before the referee was waving his arms across, signaling the goal didn't count.
After a review, replays clearly showed the puck slid across when Lehner reached back and knocked it into the net before pulling it back out.
"Three of us thought for sure (it was a goal)," Ference said, breaking into a smile. "We were celebrating. We would have looked foolish if it was called back."
Bergeron, standing in front of the Bruins' bench, pumped his fist and accepted congratulations from a few teammates before skating over to greet netminder Tuukka Rask.
Nathan Horton scored the other goal for Boston, which won its fourth straight and was coming off a 4-1 road trip. The Bruins are 13-2-2 this season.
Rask made 30 saves for the Bruins, including a pair of stellar stops in OT.
Jim O'Brien scored for the Senators, who had a five-game winning streak snapped.
Lehner, recalled from the AHL on Feb. 22 after top goaltender Craig Anderson was sidelined with a sprained ankle, stopped 44 shots.
"They threw a lot of pucks at us today," Lehner said. "Unfortunately at the end there they got a stick on it and got a lucky bounce, I think. I couldn't recover really with my blocker, so I had to take my hand out and it still got in."
Rask's stops in overtime came on point-blank bids, the second coming off the stick of Kyle Turris' one-timer with just under 2 minutes left.
With the win, Boston jumped ahead of Ottawa by a point in the Eastern Conference.
"Coming into a building like this with probably the hottest team in the conference, we played them toe to toe," Senators forward Daniel Alfredsson said.
Bruins forward Milan Lucic was whistled for closing his hand on the puck with 32 seconds left in regulation when he fell on the ice behind the Senators' net, but Rask made a nice stop on Mika Zibanejad's bid from the point.
Boston took a 1-0 lead on Horton's goal 5:48 into the second period. Lucic's hustle play kept the puck in at the left point, where he flipped it in along the boards. Horton outmuscled a Senators defenseman for the puck, setting up a 2-on-1 play with Dougie Hamilton in the slot area. Horton then slid a change-of-pace shot by Lehner.
Ottawa tied it on O'Brien's power-play goal midway into the period, snapping Boston's streak of successfully killing off penalties at 27 straight.
With Ottawa's power play in the closing seconds, Kaspars Daugavins broke in on a clean breakaway. Rask made a right pad stop before David Krejci mishandled the rebound in a scramble in front before O'Brien slipped a shot into the net.
Midway into the second, Krejci split the defense and skated in for a backhand bid he fired wide while he was being hooked by Sergei Gonchar.
A little over 2 minutes after the Senators killed off Gonchar's penalty, Boston was whistled for too many men on the ice, setting the stage for O'Brien's tying goal.
The Senators lost some key pieces to their team, including defenseman Erik Karlsson, who is out for the season with a lacerated Achilles, and center Jason Spezza, also out for the season after back surgery. Top goaltender Anderson has missed the last three games with his sprained ankle.
But it hasn't slowed their play the past two weeks.
The Senators played the Bruins through a scoreless first period despite getting outshot 11-5. Neither team had any really good scoring chances.
Lehner had his only career shutout against the Bruins exactly one year ago, a 1-0 win at TD Garden. Lehner, a backup the past two games, played in just his 14th career game. ... The Bruins opened a stretch of three home games in four days. They host Tampa Bay on Saturday and longtime rival Montreal Sunday night. ... Boston went 5-1 against Ottawa last season. ... Anderson, injured last Thursday against the Rangers, entered the night with a league-leading .952 save percentage.