Ulster have been dealt a giant blow after Nick Williams was ruled out of action for eight weeks.
The powerful No.8 suffered a knee injury in the Belfast-based province's 23-6 over Glasgow Warriors on Friday night.
He is certain to miss this weekend's Heineken Cup Pool Four clash with Castres Olympique and could be left desperately short of game time ahead of Ulster's quarterfinal.
"An assessment this morning confirmed that he sustained medial ligament damage to his left knee and is expected to be out for up to eight weeks," read an Ulster rugby statement.
Ulster can secure a home quarterfinal with a victory over Castres at Stade Pierre Antoine.
Both wing Craig Gilroy and fly-half Paddy Jackson also suffered injuries against Gloasgow but Ulster are confident they will recover in time for the trip to France.
"He will be subject to an ongoing conservative management programme and will be reviewed in due course," the statement continued
"Outhalf Paddy Jackson was assessed yesterday for an ankle injury he picked up against Glasgow, as was winger Craig Gilroy who suffered a bang to the head on Friday night.
"Jackson's ankle is responding well to physiotherapy treatment, while Gilroy is following the necessary return-to-play protocol.
"It is hoped that both players will be available for selection for this weekend's Heineken Cup game against Castres Olympique."
