After a full season of brilliance, Tim Thomas’ best save was among his last — so far.

Protecting a one-goal lead with 10:42 left in Monday’s Game 5 of the Eastern Conference finals, Thomas’ lunging stick save on an otherwise certain goal by Steve Downie might go down as the Bruins’ play of the year — shades of Reggie Lemelin against Pat Verbeek in 1988 — especially if it finally points the way to that elusive Stanley Cup.

The Bruins can earn a trip to the finals with a victory in tonight’s Game 6 in Tampa. They know full well their goaltending advantage has gone from negligible at series’ start to overwhelming at the end.

“Wow, it’s pretty special when your goalie makes those kind of saves,” said Nathan Horton, who scored the first goal in Monday’s 3-1 victory. “It really picks you up. He never gives up, that’s what good about him. Definitely, Timmy stepped up for us.”

Lightning coach Guy Boucher decided yesterday to go back to Dwayne Roloson for Game 6 after starting Mike Smith on Monday. The 41-year-old Roloson, who was brilliant in the Lightning’s first two series, has struggled mightily against the Bruins, being pulled from two of the first four games.

Thomas, although struggling at times himself in the first four games, made 33 saves Monday, including 13 in the first period, allowing the unusually tight Bruins to emerge with just a one-goal deficit.

But even with Thomas at his best, the Bruins cannot afford another shaky start tonight.

“It’s going to take our best game,” Claude Julien said. “We can’t be tight. We’ve got to go out there and play with a purpose.”