Phil Kessel had two goals, including an empty-netter with less than second remaining, for the Bruins, 12-1-1 since the start of November. Tim Thomas made 30 saves to improve to 7-1-1 in his last nine starts.
"It was a tight hockey game," Krejci said. "I think we played good in the second and third periods. We were all over them, and we deserved to win. I was just hoping that we were going to score, and I'm glad that it was me."
Martin St. Louis had the Tampa Bay goal. The struggling Lightning have lost six in a row and 13 of 15.
"It seems like we're waiting for something bad to happen," Tampa Bay coach Rick Tocchet said. "We played hard. We have no margin for error it seems like."
After taking a pass from Blake Wheeler, Krejci made a couple nice moves before beating goalie Mike Smith with 11:13 left. Krejci has goals in three straight games and also has a seven-game points streak (five goals, 11 points).
"That was beautiful," Thomas said. "As a goalie, I try to stay even keeled, but when a guy pulls off a move like that and puts us ahead, I got excited. I couldn't help it. I had to tap my stick on the ice and give him credit. That was one heck of a move, and then to finish it makes it really memorable because if you pull that move and then you don't score, nobody remembers it."
St. Louis put the Lightning ahead 1-0 from the low slot at 1:21 of the first. Vincent Lecavalier set up the goal, which made him Tampa Bay's career assists leader with 340.
"I know the guys are dejected," Tocchet said. "We need to find scoring somehow."
Kessel tied it at 1 when he extended his goal streak to four games at 12:21 of the second. He has eight goals and 13 points during a 10-game point streak.
Smith stopped 23 shots.
"We've talked about it before, and we can talk about it all we want. Coaches can't play for us on the ice. Management can't go play for us on the ice," Smith said. "It's the guys in here that got to step up to the plate."
Notes: Bruins LW Marco Sturm (concussion) resumed practicing this week, but missed his seventh straight game. ... Boston C Marc Savard had two assists, giving him 14 assists and 16 points in his last 10 games. .. Tampa Bay recalled D Matt Smaby from Norfolk of the AHL. ... Boston D Aaron Ward (leg) didn't play and is also expected to miss Saturday's game at Florida. ... Brad Richards, now with Dallas, had 339 assists while with the Lightning.