Tim Thomas drifted to the front of the crease to cut down the angle, leaving him out of position when the shot went wide to his right, off the boards and right to Lightning forward Steve Downie.
The Boston goalie reached back, swung his stick at the puck and caught it with the bottom edge of his blade, knocking it away to protect a one-goal lead and give the Bruins a 3-1 victory over Tampa Bay that left them one win away from their first Stanley Cup finals since 1990.
"It was just reaction and, you know, desperation," Thomas said after stopping 33 shots last night - none bigger than Downie's with about 11 minutes left and Boston protecting a one-goal lead. "I'll admit I got a little bit lucky there."
Thomas bounced back from a Game 4 collapse, and Brad Marchand scored the game-winner to help give Boston a 3-2 lead in the best-of-seven, Eastern Conference finals.
The Bruins could clinch the series tomorrow night in Tampa Bay.
"Our goal right now is to not play a Game 7," Bruins coach Claude Julien said. "It's going to take our best game."
The Lightning would need to win Game 6 to force a decisive game in Boston on Friday. Tampa Bay faces elimination for the fourth time in these playoffs, having fallen behind the Penguins, 3-1, in the first round.
"Our backs were against the wall before against Pittsburgh," forward Ryan Malone said. "We're not going to be able to win two games in one game. So you try to go out there, worry about the first 5 minutes of the game and you take it from there."
Simon Gagne, who scored the game-winner for Tampa Bay in Game 4, scored only 69 seconds in. Nathan Horton tied it for Boston in the second period, 17 seconds after returning from the penalty box. Marchand scored with 4:04 left in the period to give Boston a 2-1 lead.
Tampa Bay finally managed to pull the goalie with 42 seconds left, but Rich Peverley scored an empty-netter with 12.1 seconds remaining to clinch it.
Boston managed only 19 shots on Mike Smith as he made his first career playoff start in place of Dwayne Roloson.
Smith said he didn't expect to play.
"I figured that Rollie would be back in," he said. "He's done well the whole playoffs. I was ready to go if called upon. Rollie's been great, he's been here and done this and any advice that he gives me is stuff that I just suck in like a sponge. Obviously, he's a great mentor."
* San Jose Sharks captain Joe Thornton is expected to play a potential elimination game in Game 5 of the Western Conference final despite leaving the previous game with an injury.
Thornton was hurt on a shoulder-to-shoulder check by Raffi Torres in the third period of a 4-2 loss to the Vancouver Canucks on Sunday that put the Sharks in a 3-1 series hole. He did not return to the game and did not take part in an optional practice yesterday before the team flew to Vancouver for tonight's game.
But coach Todd McLellan said he expects Thornton to play, even if he is not 100 percent. Thornton was not available to the media, but told McLellan he will be ready to play.
"When Joe Thornton comes to you and tells you he's playing, he's playing," McLellan said. "That can happen in exhibition season, that can happen at . . . a charity game in the middle of the summer."