Paddy Wallace has been ruled out of Ulster's Pro 12 match against Munster at Ravenhill on Friday.
A quad injury looks set to sideline Wallace for three weeks. It means that he will also miss the crucial Heineken Cup clashes against Montpellier and Leicester Tigers.
The centre only recently returned from a nine-month lay-off with an ACL injury.
There was better news for Ulster coach Mark Anscombe, with the return of injured trio Chris Henry, Iain Henderson and Nick Williams.
Captain Johann Muller, who was rested for the game against Leinster last weekend, is expected to take his place against Munster.