Bath and Springbok star flanker Francois Louw injured his left knee playing against New Zealand on Saturday.
The flanker walked off the field just after the first ten minutes in South Africa's 57-15 defeat to New Zealand. Louw is one of many injuries to hit the club including David Denton who has a long-term injury and will be out till the beginning of next year.
Welsh international Taulupe Faletau has also been ruled out for three weeks with a ligament injury.
There is more bad news for Bath after England international Anthony Watson was injured after Bath's 30-3 win over Sale on Friday.
Director of rugby Todd Blackadder bemoaned the loss of Watson.
"I'm so disappointed for him… He's just absolutely gutted at the moment," Blackadder told the Bath Chronicle.
"He could possibly miss the November internationals, I'm not sure."
A statement on the extent of Louw's injury is expected on Tuesday or Wednesday.