Lewis Moody will be out of action for 10 to 12 weeks after undergoing shoulder surgery.
Moody, 33, suffered the injury during Bath's 16-7 Aviva Premiership defeat to Worcester on November 25.
The former England captain has also been sidelined by eye and knee injuries since moving from Leicester to Bath last year, limiting him to just 13 league appearances and four in the Heineken Cup.
Moody was making only his third appearance for Bath since returning from the World Cup when he was injured.
"I'm just gutted for the player himself,'' Bath assistant coach Brad Davis told BBC Radio Bristol.
"He came back enthusiastic in training but I'm sure he's going to give loads off the field now to keep himself occupied.
"It's disappointing but what can you do? He's always played the game that way, he's always going to pick up knocks.''