Commenting on Friday's match, head coach Matt Williams said: "The Ospreys are a fantastic team, a brilliant team and physically they are a massive side.
"No one expects us to win. Everyone has written us off, everyone says we can't do it, so this is a week when there is not a lot of pressure on us, and that is a good thing."
Grand Slam winner Stephen Ferris, Paul Steinmetz and Bryn Cunningham were not considered due to injury.
Although tickets for the Main Stand and Terrace at Ravenhill have now sold out, there are still tickets available for the Ospreys game, within the Promenade and YellowTom areas of the ground.
A limited number of tickets will also be available to purchase on the gates on match night.
ULSTER Squad (v Ospreys): Backs (12) - Simon Danielli, Andrew Trimble, Darren Cave, Cillian Willis, Niall O'Connor, Clinton Schifcofske, Ian Whitten, Isaac Boss, Ian Humphreys, Timoci Nagusa, Mark McCrea, Paddy Wallace.
Forwards (12) - BJ Botha, Tom Court, Bryan Young, Ed O'Donoghue, Matt McCullough, Carlo Del Fava, Chris Henry, Nigel Brady, David Pollock, Rory Best, Ryan Caldwell, Robbie Diack.