Updated

TAMPA, Fla. -- Martin St. Louis and Teddy Purcell each scored twice, resilient goalie Dwayne Roloson weathered a hat trick by Boston's David Krejci, and the Tampa Bay Lightning stayed alive in the Eastern Conference finals with a 5-4 win over the Boston Bruins in Game 6 on Wednesday night.

Game 7 is Friday night in Boston. The Bruins are seeking their first trip to the Stanley Cup finals in 21 years, and the Lightning will try to clinch their first appearance on hockey's biggest stage since they won their only NHL championship in 2004.

The Western Conference champion Vancouver Canucks await the winner in the finals.

St. Louis also assisted on a third-period goal that put the Lightning up 4-2. His second goal -- and NHL-leading 10th of the playoffs -- restored Tampa Bay's two-goal lead after Boston pulled within 4-3 on one of two goals Krejci scored to keep the Bruins within striking distance in the closing minutes.

Roloson, who didn't play in Game 5 after being pulled from two of the previous three games because of ineffectiveness, also gave up a pair of first-period goals and finished with 16 saves.

Boston's Tim Thomas gave up another early goal, then struggled after Krejci and Milan Lucic scored to give the Bruins a 2-1 lead through one period.

The Lightning took control when St. Louis, Purcell and Steven Stamkos scored power-play goals within a 12-minute span of the second and third periods.

Roloson improved to 7-0 in elimination games during his career, including 4-0 this postseason. The Lightning rallied from a 3-1 deficit to beat Pittsburgh in the first round, with their 41-year-old goalie shutting out the Penguins in Game 7 on the road.

Tampa Bay coach Guy Boucher gave backup goalie Mike Smith his first career playoff start Monday night, saying he felt Roloson -- whose midseason acquisition was one of the keys to Tampa Bay emerging as a contender -- needed a "breather" after starting the Lightning's first 15 postseason games.

Smith stopped 17 of 19 shots in the Game 5 loss, however Boucher didn't hesitate to go back to Roloson with the Lightning facing elimination.

"Personally, I don't like the word desperation. ... To me, it's just another game," Roloson said following the Lightning's skate Wednesday morning. "You have to focus on your job."

Boston coach Claude Julien said his team would need to play its best game of the series to clinch it, and the Bruins certainly had to have some doubt about how the night might go when Vincent Lecavalier won a faceoff in the right circle and Purcell scored on Tampa Bay's opening shot.

Lucic countered for Boston less than seven minutes later with a wrist shot from the slot that got past Roloson. Krejci's third goal of the series, after he took a nice backhand pass from along the boards from Daniel Paille, gave the Bruins a 2-1 lead with 3:30 remaining in the first period.

But an inability to take advantage of three more power-plays caught up with Boston in the middle of the second period when Tampa Bay, which hadn't scored in man-advantage situations since Game 2, converted three within 12 minutes to regain the lead for good.