"Tuukka was in this morning. He will be getting treatment. He will not play this weekend, and then we'll go from there," Bruins head coach Bruce Cassidy said after Friday's practice at TD Garden.
"I don't think there's anything major there, but obviously something's going on where he had to leave the game again with a similar injury to last time."
Thursday's game was Rask's first appearance in net since leaving the team's March 7 matchup versus the New Jersey Devils due to an injury.
The Bruins' next game is Saturday afternoon versus the last-place Buffalo Sabres, followed by a two-game set against the New Jersey Devils on Sunday and Tuesday.
Jaroslav Halak will be Boston's No. 1 goaltender in Rask's absence, and Dan Vladar likely will serve as the backup.