Ballymena front rower Andrew Warwick has been included in the preliminary squad for the first time. The 21-year-old has previously represented Ulster at Schools, Under-20 and Ravens levels and may now get an opportunity to line out for the senior side this weekend.
Luke Marshall has returned from injury and should play some part on Friday night, while Ireland Under-20 starlet Stuart Olding has also been included among the backs.
Ulster still hold an 11-point gap at the top of the RaboDirect PRO12 after suffering just one defeat in the opening 13 rounds of the competition - a 24-10 loss away to Munster in December.
The Ospreys have now gone four successive matches without a win in all competitions. However, in the league, the Welshmen have suffered just one reversal in their last ten encounters.
Ulster have already beaten the Ospreys in Swansea in round 2 this season and are going for a first ever season's double over the Welsh region.
ULSTER Squad (v Ospreys) - Backs (11): Ruan Pienaar, Paul Marshall, Niall O'Connor, Stuart Olding, Paddy Wallace, Luke Marshall, Darren Cave, Michael Allen, Andrew Trimble, Chris Cochrane, Ricky Andrew.
Forwards (14): Nigel Brady, Rob Herring, Niall Annett, Callum Black, Ricky Lutton, Andrew Warwick, Tom Court, Lewis Stevenson, Dan Tuohy, Neil McComb, Johann Muller (capt), Mike McComish Robbie Diack, Ali Birch.