Ulster centre, Luke Marshall, will undergo an operation on a briken finger on Wednesday ruling him out of Ulster’s last two Pool Four matches in the Heineken Cup.
Marshall suffered the injury during the first half of last week’s RaboDirect PRO12 47-17 win over Scarlets in Belfast on January 4.
The injury is not expected to keep him out of selection to the Irish National squad ahead of the Six Nations Championship, if Ireland coach, Declan Kidney was to have included him.
Meanwhile, Ulster coach, Mark Anscombe, said the situation was 50:50 with regard to lock Dan Tuohy being fit to face Glasgow Warriors in Friday night’s penultimate Pool Four match at Ravenhill.
Tuohy was forced off just before half time in last Friday’s game with a recurrence of a calf injury. He had just returned to the side from injury.
Fullback, Jared Payne, also remained a doubt, but Anscombe was more hopeful he would be fit again after a troublesome groin strain kept him out of last week’s fixture.
Tuohy and Payne were both included in Tuesday’s provisional squad with Anscombe adding: “We will give them every possible chance and hopefully time will be on our side.”
Adam D’Arcy is added to Ulster’s injury woes at fullback, ruled out after taking a heavy knock early on against Scarlets.
Ricky Andrews would have been a likely candidate but he is not registered for the ERC competition, which leaves the Irish Province light at fullback cover this weekend.
ULSTER PROVISIONAL SQUAD
Forwards (16):Callum Black, Tom Court, Declan Fitzpatrick, Adam Macklin, John Afoa, Rob Herring, Rory Best, Lewis Stevenson, Dan Tuohy, Iain Henderson, Neil McComb, Mike McComish, Chris Henry, Robbie Diack, Roger Wilson, Nick Williams.
Backs (11): Ruan Pienaar, Paul Marshall, Michael Heaney, Paddy Jackson, Paddy Wallace, Darren Cave, Michael Allen, Craig Gilroy, Andrew Trimble, Chris Cochrane, Jared Payne.