BOSTON — Stop me if you’ve heard this one before.

Tim Thomas gets a start. Tim Thomas plays great. Tim Thomas gets a second straight start and plays so poorly he gets the hook.

A chart of Thomas’ play this season would look a lot like a drawing of the Rocky Mountains at this stage of the season, and he hit a new low against Buffalo tonight with three goals allowed on 14 shots at TD Garden.

“I guess,” Thomas replied when asked if this was just one of those nights. “It is what it was.”

Granted, the goals weren’t all his fault. Dennis Wideman’s attempt to block the first goal on a point shot by Tyler Myers involved letting the puck go between his arm and his body, and the second score deflected off Wideman after a juicy rebound. You could almost forgive Thomas for the third goal, even, if Thomas didn’t get a piece of Tim Kennedy’s shot and then allow it to trickle in through the 5-hole. That goal convinced head coach Claude Julien to pull last year’s Vezina Trophy winner — although the coach said he was trying to change the momentum rather than blame Thomas.

“You’d like to stay in a game and battle it out. It’s not fun getting pulled,” said Thomas.

On came Tuukka Rask, who entered the game with a 1.72 goals-against average and .944 save percentage in four games vs. Buffalo this season. Rask stopped all 19 shots he faced, including breakaways by Derek Roy and Jason Pominville. To top it all off, Rask assisted on Boston’s second goal.

Julien explained his decision to go with Thomas over Rask as a combination of Thomas’ play in a shutout over Calgary Saturday and a desire to have two fresh goaltenders play in both halves of Boston’s back-to-back situation against Buffalo and at New Jersey Tuesday. Now he better hope that Rask can make that decision pay off in Newark after Thomas failed at home. And it might be time to throw out all the reasoning and play the rookie who’s competing for both the GAA and save percentage titles for the entire NHL.