TORONTO -- David Krejci saw his chance and didn't hesitate.
Presented with an opportunity on an odd-man rush after a mistake by the Toronto Maple Leafs, Krejci let go with a 34-foot wrist shot that beat goaltender James Reimer in overtime as the Boston Bruins took command of the first-round playoff series.
Krejci's third goal of the game came at 13:06 of the first overtime Wednesday at Air Canada Centre and gave Boston a 4-3 victory and a 3-1 lead in the series.
"I just tried to shoot it," said Krejci, who has five goals in the series. "In overtime there's no bad shot so it wasn't a perfect shot but it went in."
It also was a less-than-perfect play that led to the game-winning breakout. The Maple Leafs had been taking it to the Bruins in the overtime.
"I thought in overtime we were attacking and definitely taking the puck and the play to the net," Maple Leafs head coach Randy Carlyle said. "That's what we designed. In our minds we were doing the things we thought we needed to do but we made a mistake.
"You can't afford to make mistakes that lead to odd-man rushes. We turned the puck over deep in the corner and then we pinched and gave them an odd-man rush and they scored a short-side goal. To me that feels like a dagger after the effort was put forth by our group."
Leaf captain and defenseman Dion Phaneuf pinched in on the play that gave Boston its big chance.
Reimer said he played it the way he wanted, facing the shooter and holding his angle.
"I pretty much would have played it the same but it just squeezed through," Reimer said.
"Obviously (Krejci's) line has been good all series and tonight certainly he was the guy shining and he's on top of his game," Bruins head coach Claude Julien said. "He's been a real good playoff performer for years.
"He doesn't shy away from traffic. He doesn't shy away from the physical game. He's very gritty when he needs to be gritty so if he's got one weakness, he's really hard on himself at times when things aren't going well but when you see him playing like that I'm not sure you want to call it a weakness."
Zdeno Chara had four assists for the Bruins.
The Bruins overcame a 2-0 first-period disadvantage to take a 3-2 lead in the second period on Krejci's second goal of the game. But Clarke MacArthur soon tied it and the game went into overtime after a goalless third period.
The winning goal came after a wide-open overtime in which the Maple Leafs had their chances.
Patrice Bergeron also scored for the Bruins. Joffrey Lupul and Cody Franson scored for Toronto.
Reimer stopped 41 of 45 shots. Tuukka Rask stopped 45 of 48 shots in the Boston goal during regulation.
"We controlled the pace of play and just couldn't get one to go," said Lupul, who was a victim of one of Rask's good saves.
The Maple Leafs started well and scored at 2:35 of the first period on a 27-foot wrist shot by Lupul, his third goal of the series, after Phil Kessel whirled behind the goal and put a pass in front from the corner.
The Leafs took a 2-0 lead with an even-handed goal at 18:32 on a 61-foot wrist shot from the right point by Franson, his first of the series.
The Bruins ended the first period with a man advantage after Leo Komarov was sent off for charging at 19:10.
The Bruins took advantage with a power-play goal by Bergeron at 32 seconds of the second period, a 17-foot snap shot to cut the lead to 2-1. Bergeron's first goal of the series followed Reimer's save on a 65-foot slap shot by Chara. Milan Lucic picked up an assist, giving him at least one point in all four games.
"We talked about it between periods to get that goal right away and get back in the game," Bergeron said. "It was definitely something that we needed to do early in the second."
The Bruins tied the game 2-2 at 12:59 when Krejci scored on a 32-foot wrist shot.
With Colton Orr off for elbowing Chara, Krejci scored again at 16:39 on the power play, snapping home a 41-footer for his fourth goal of the series.
But the Leafs responded at 17:23 with a goal by MacArthur, his first of the playoffs. He snapped home a puck that sat invitingly 30 feet away and directly in front of the Boston goal.
Leafs defenseman Mark Fraser took a puck to the head and was having a scan as a precaution.
NOTES: The Bruins won Game 3 on Monday 5-2 although the Maple Leafs outshot them 18-6 in the third period and 47-38 overall. ... Bruins scratches on Wednesday were Dougie Hamilton, Kaspars Daugavins, Jay Pandolfo, Carl Soderberg and Aaron Johnson. Maple Leafs scratches were John-Michael Liles, Joe Colborne, Frazer McLaren, Ryan Hamilton and Michael Kostka, who picked up a finger injury in the opening game. ... This is the 14th playoff series between the teams with the Leafs holding an 8-5 advantage. ... Game 5 will be played on Friday at Boston.