Ulster may be without forwards Iain Henderson and Steven Kitshoff for Saturday's Challenge Cup quarter-final clash with Clermont.
The duo were injured in the last-16 win over Montpellier on Sunday.
Ireland lock Henderson has a foot injury, while prop Kitshoff, who will leave at the end of the season to return to the Stormers, has an ankle injury.
The club say they will be assessed during the week to determine their availability.
However, Richie Murphy will be able to welcome back Mike Lowry (concussion), Jacob Stockdale (illness) and Tom Stewart (injury).
Marty Moore, Kieran Treadwell, Callum Reid, Ben Moxham, and Billy Burns remain unavailable through injury.
Clermont, currently 11th in the Top14, beat Cheetahs 27-22 in their last-16 game and welcome Ulster to the Parc des Sports Marcel Michelin on Saturday at 12.30pm.
Meanwhile, Munster have announced the departures of Neil Cronin (above), Colm Hogan and Andrew O’Mahony, who have completed their time at the province.
Scrum-half Cronin scored two tries in 39 Munster appearances since making his debut as a non-contracted player against Leinster in December 2014.
Back-three player Hogan departs after helping Munster to victories over Harlequins and Crusaders in February having joined on a short-term contract in November.
Scrum-half O'Mahony departs having completed his two-month contract with the province.
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