Ulster centre Luke Marshall and full-back Adam D'Arcy have been sidelined after suffering injuries in the PRO12 win over Scarlets at the weekend.
Both will miss Ulster's Heineken Cup tie against Glasgow (Live on RTÉ Radio 1, 8.00pm) at Ravenhill on Friday as a result.
Marshall will have surgery on a fractured finger and be sidelined for 4-6 weeks, while D'Arcy fractured his ankle and will see a specialist later in the week to find out the extent of damage done.
Dan Tuohy, who suffered a recurrence of a calf injury against Scarlets, has been named in Ulster's preliminary Heineken Cup squad for Friday's clash 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.