Nick Williams and Ian Porter have been ruled out Friday's RaboDirect PRO12 match against Edinburgh at Ravenhill after they both picked up injuries in training.
Williams suffered a recurrence of the calf injury that he sustained last month, while Porter is out with a shoulder injury.
As a result, Roger Wilson is promoted from the bench to the starting XV, with Mike McComish now named as a substitute.
With Michael Heaney also unavailable due to injury (AC joint), Hughes Insurance Ulster Academy scrumhalf, David Shanahan, is named as one of the replacements.
The Ireland U20 player is in line to make his first appearance for the senior Ulster side if called upon.
Ulster XV and replacements to face Edinburgh (KO 7.05pm)
(15-9): C Gilroy, A Trimble, D Cave, L Marshall, M Allen, J McKinney, P Marshall; (1-8): C Black, R Herring, J Afoa, L Stevenson, I Henderson, R Diack (Captain), S Doyle, R Wilson; Replacements (16-23): N Annett, T Court, R Lutton, D Tuohy, M McComish, D Shanahan, P Nelson, R Andrew.