Ulster's Marcell Coetzee is set to be out of action for nine months. The flanker, who has only played once this season, returned to South Africa for further surgery on his left knee.
"He has had recurrent left knee problems because of a laxity in his previously repaired ACL," Ulster said in a statement.
"And to repair this he has had revision surgery performed on this ligament. His anticipated return to play time is nine months."
The 26 year-old arrived in Belfast in 2016 on a three-year-deal but has struggled with fitness since then, making only five appearances for Ulster. His contract runs until the end of the 2018-2019 season.
In other injury news, Chris Henry sustained trauma to his larynx in the game against Connacht and was unavailable for selection but Ulster are hopeful he will be fit for next week.
Alan O'Connor sustained a concussion in the game against Connacht and is following return to play protocols.