Sonny Parker comes in for Andrew Bishop at 13, whil Ian Gough plays ahead of Alun Wyn Jones, and Ryan Bevington starts at loosehead.
Coach Sean Holley has told his players they have to put Saturday's disappointment behind them as they look to secure a place in the Magners League play-offs.
"After the disappointment of Saturday, we've got to be professional and really show what we are made of by getting straight back into it. With two tough games this week we can't feel sorry for ourselves. We've put ourselves in a position where we are challenging for one of the play-off spots, so our focus has to be on that now," Holley said.
"It's a quick turnaround from Saturday, which will be a test of our fitness and conditioning, as well as our character and spirit. It's never easy going out to Ravenhill, where we can expect a passionate crowd and a side that will make life very difficult for us. We've shown in that past that we can win out there, and we know that's what we've got to do if we want to reach the play-offs.
"We've everything to play for these next few weeks, and will be going to Ireland with a positive attitude. We can be proud of how we performed as a team against Biarritz, we went there looking to play a positive style of rugby, to keep the ball alive and I think we achieved that. We created some great opportunities and scored some good tries, but ultimately, we lacked that clinical edge at some important times.
"We mustn't allow ourselves to dwell on the defeat though. We have to take the disappointment and pain of that defeat, and use it to push us forward over the next few weeks and look to end the season on a high note."
Ospreys team to face Ulster
15 Lee Byrne, 14 Tommy Bowe, 13 Sonny Parker, 12 James Hook, 11 Shane Williams, 10 Dan Biggar, 9 Mike Phillips, 1 Ryan Bevington, 2 Huw Bennett, 3 Adam Jones, 4 Ian Gough, 5 Jonathan Thomas, 6 Jerry Collins, 7 Marty Holah, 8 Ryan Jones (Capt)
16 Ed Shervington, 17 Paul James, 18 Alun Wyn Jones, 19 Filo Tiatia, 20 Jamie Nutbrown, 21 Andrew Bishop, 22 Nikki Walker