Injury has forced Ulster head coach Mark Anscombe to omit Luke Marshall (finger) and Adam D’Arcy (ankle) from his provisional 27-man squad for Friday’s Heineken Cup Pool 4 clash against Glasgow at Ravenhill (8pm).
Both players picked up knocks during Ulster’s 47-17 PRO12 win over Scarlets at the weekend.
Centre Marshall will have surgery on a fractured finger and will be sidelined for 4-6 weeks, while D’Arcy fractured his ankle.
The fullback will see a specialist later in the week when an approximate timeframe for a return to action will be confirmed.
Dan Tuohy, who suffered a recurrence of a calf injury against Scarlets, has been named in the squad and will be monitored throughout the week.
Jared Payne, who missed the game against the Welsh outfit with a groin strain, is also included and could play some part on Friday.
It is all to play for in Pool 4, although Ulster, the 2012 finalists, are in the box seat, three points clear of Castres Olympique.
Northampton are five points adrift of Ulster but both will be wary of their away trips in Round 6 to Glasgow and Castres respectively.
Glasgow are yet to register a win despite coming close on all four occasions, especially in their nail-biting back-to-back games against Castres.
Glasgow have two victories to Ulster’s one in the history of this Heineken Cup fixture after the Irish Province triumphed 19-8 at Scotstoun earlier this season.
The Scots have just four wins and a draw to their name from 42 away matches in the Heineken Cup. One of those wins came at Ulster (1997), their only win away in Ireland.
Provisional Ulster Squad (v. Glasgow)
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.
Ruan Pienaar, Paul Marshall, Michael Heaney, Paddy Jackson, Paddy Wallace, Darren Cave, Michael Allen, Craig Gilroy, Andrew Trimble, Chris Cochrane, Jared Payne.