BOSTON (AP) -David Backes didn't swing and miss on his team's last chance.
With the clock winding down and the Blues close to yet another road loss, Backes saw the puck pop up in front of him. Positioned at the right post, he batted it out of the air and into the net as the siren sounded.
After a lengthy replay review, the goal counted. The puck was slightly above the cross bar when Backes hit it, the video showed.
"I tried not to watch the replay too many times. But no matter what I saw, I had a bias toward that one," Backes said. "I'm going to have my bias toward that one and say it was a good call."
Down 4-2, the Blues started their comeback with David Perron's power-play goal with 1:20 left.
T. J. Oshie and Brad Boyes scored in the shootout for the Blues, who have the worst record in the Western Conference and had lost nine of their previous 10 road games.
The Eastern Conference-leading Bruins trailed 2-1 before scoring three times in a span of 1:39 late in the third period.
"I guess the best way to describe it is everyone involved except for the people in charge don't happen to think it was a goal," said Boston coach Claude Julien, who later went on to say, "we got what we deserved."
Boston's P.J. Axelsson and Michael Ryder had power-play goals 19 seconds apart, then Zdeno Chara scored off a faceoff with 3:05 left for a 4-2 edge.
Blues reserve goaltender Chris Mason stopped Blake Wheeler and Axelsson in the shootout.
Wheeler also missed an empty net with about 20 seconds left in regulation before Backes scored.
"It was any hockey player's worst nightmare come true," Wheeler said of his shot from just outside the blue line. "It definitely hurts just to know how hard these guys fought all game to get back and pretty much get the win. To have it fall on my shoulders hurts pretty bad."
Mason kept the Bruins scoreless after replacing injured starter Manny Legace midway into the opening period until the late rally. Legace left with what the team called a lower body injury and wasn't on the bench for the remainder of the game.
"To our credit, it was a heck of a finish. We didn't give up," Mason said. "We could've easily packed it in there and game over. We got lucky there and found a way to do it."
St. Louis had taken a 2-1 edge when Jay McClement one-timed a shot inside the left post 6:51 into the second. There was a smattering of boos as the Blues controlled play midway into the period.
Neither team had a shot on goal until Boston made it 1-0 on Chuck Kobasew's goal 4:26 into the game.
The Blues tied it at 1 when Brad Winchester redirected Jeff Woywitka's shot from the point and the puck trickled between Tim Thomas' pads at 7:37. Thomas, on his knees, looked up to the ceiling in frustration after the puck slid behind him.
Bruins defenseman Shane Hnidy saved a goal when he reached behind Thomas and pulled out a loose puck out with his stick just before it rolled over the line in the first.
Notes: Bruins LW Milan Lucic missed his sixth straight game with an undisclosed injury and D Aaron Ward was out for his third consecutive with what the team called a charley horse sustained Jan. 13 against Montreal. Ward did leave that game, though, after being hit from behind into the boards by the Canadiens Andrei Kostitsyn. ... It was the final meeting of the teams this season. Boston beat the Blues 6-3 in St. Louis on Dec. 21. ... It was the opener of a day-night, hockey-basketball doubleheader. The Celtics were to play the Phoenix Suns at night.