Experienced centre Wallace injured an ankle during last Saturday's game, while flanker Faloon took a bang to his shoulder.
It remains to be seen if the pair will be fit to make the matchday squad, which will be confirmed on Thursday afternoon.
Ulster coach Brian McLaughlin said: "Although we beat the Ospreys in Swansea at the start of the season, we all know not to underestimate them.
"The Ospreys are a dangerous side who can and do compete at the highest level, we need to ensure we give them nothing to play with.
"At training this week we will work hard in certain areas of the pitch, the focus will be to put down our patterns of play, after that, on the day, it's just a matter of us holding onto the ball and making the best use of any chances we have. We must put them under pressure.
Only six points separate Ulster from the Ospreys in an extremely tight and competitive Magners League table, ahead of the final league matches before the Six Nations break.
Tickets for Friday's game are available from the Ravenhill Ticket Office (Monday-Thursday, 9am-5pm, Friday, 9am-4pm), the Ticket Line, tel: 02890 493 222 Option 2 (Monday-Friday, 10am-12pm) or by clicking here.
ULSTER Squad (v Ospreys) - Backs (13): Jamie Smith, Clinton Schifcofske, Simon Danielli, Darren Cave, Ian Whitten, Timoci Nagusa, Ian Humphreys, Niall O'Connor, Isaac Boss, Paddy Wallace, Andrew Trimble, Cillian Willis, Jonny Shiels.
Forwards (15): Declan Fitzpatrick, Bryan Young, BJ Botha, Nigel Brady, Andy Kyriacou, Ed O'Donoghue, Dan Tuohy, Ryan Caldwell, Chris Henry, Tom Court, Stephen Ferris, Willie Faloon, Thomas Anderson, Neil McComb, David Pollock.