Butch James has undergone surgery to stabilise his right shoulder, ruling the World Cup winner out of the opening two rounds of the Heineken Cup.
James picked up the shoulder injury in the Springboks' Tri Nations defeat to Australia and returned to the UK to visit specialists and he is now not expected to feature for the West County side until November.
The fly-half was out of action for 10 weeks at the beginning of 2008 with an injury to the same shoulder and Bath will hope that James is fully fit for the back-to-back fixtures against Ulster in December.
"It is always frustrating to lose a player of Butch's influence, but we will make sure he receives the best care and attention to get him back with the squad as and when he's ready," said Bath head coach Steve Meehan.
"But we have a strong squad at inside backs and we are confident that we would be able to handle his absence."
James will miss the former European champions face Biarritz Olympique in their first Pool 4 game on Sunday, October 10 as well as the fixture in Italy against Aironi Rugby the following week.