Bath star Butch James will be sidelined until November after undergoing surgery on his right shoulder.
South Africa international James, 31, was hurt after going on as a replacement during the Springboks' Tri-Nations clash against Australia last month.
"It is always frustrating to lose a player of Butch's influence," said Bath head coach Steve Meehan. "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."
Bath have started their Aviva Premiership campaign with wins against Leeds Carnegie and London Irish, but the latter victory was achieved at a cost.
Four players - England internationals Matt Banahan, Lee Mears and David Flatman, plus Scotland's Simon Taylor - all went off during the Irish clash and could be sidelined for Friday night's appointment with Northampton at Franklin's Gardens.
Bath currently head the Premiership by a point from Northampton.