Ulster are without Ruan Pienaar, Stuart McCloskey and Wiehahn Herbst for Saturday's vital Champions Cup tie with Oyonnax, live on Sky Sports 5 HD.
Springboks scrum-half Pienaar has been ruled out by illness, Herbst has a foot injury and McCloskey is rested after playing all 16 of the province's matches this season.
Ireland captain Rory Best has been unable to train fully this week due to minor back tightness and is named among the replacements, with Rob Herring coming in to skipper the side at hooker.
Darren Cave replaces McCloskey at centre for his first start since the beginning of December, Paul Marshall partners Paddy Jackson at half-back while Nick Williams makes a welcome return at No 8.
Ulster require a bonus-point victory at Kingspan Stadium to keep their quarter-final hopes alive but they also need a number of other results to go their way.
"We're optimistic that we can get the job done and with the unpredictability of this competition, there's a real chance for us to go through," said Ulster director of rugby Les Kiss.
"Hopefully there will be a good crowd at Kingspan and we can give them something to cheer about."
Ulster overturned a 23-0 half-time deficit to defeat Oyonnax on January 10, but their last-eight hopes hang in the balance after coming away empty-handed from Allianz Park last weekend.
While Ulster were losing at Saracens, Oyonnax overturned Toulouse for their first ever Champions Cup victory, and they have made 14 changes to their starting XV for the trip to Belfast.
Only lock Geoffrey Fabbri retains his place while former Ulster forward Pedrie Wannenburg starts at No 8 on his return to Belfast.
"They are a good team and they will provide a big challenge for us," said Kiss.
"We need to stay focused on our game, make our tackles, start the match with the right attitude and play with discipline, because they can hurt you if you give the ball away easily. They showed that last week against Toulouse and against us a fortnight ago."
Ulster: 15 Jared Payne, 14 Andrew Trimble, 13 Darren Cave, 12 Luke Marshall, 11 Craig Gilroy, 10 Paddy Jackson, 9 Paul Marshall; 1 Kyle McCall, 2 Rob Herring (c), 3 Ricky Lutton, 4 Alan O'Connor, 5 Franco Van Der Merwe, 6 Robbie Diack, 7 Sean Reidy, 8 Nick Williams.
Replacements: 16 Rory Best, 17 Callum Black, 18 Bronson Ross, 19 Clive Ross, 20 Roger Wilson, 21 David Shanahan, 22 Ian Humphreys, 23 Rory Scholes.
Oyonnax: 15 Florian Denos (c), 14 Daniel Ikpefan, 13 Guillaume Bousses, 12 Alaska Taufa, 11 Dug Codjo, 10 Rory Clegg, 9 Julien Blanc; 1 Soane Tonga'uiha, 2 Thomas Bordes, 3 Giorgi Vepkhvadze, 4 Leon Power, 5 Geoffrey Fabbri, 6 Valentin Ursache, 7 Pierrick Gunther, 8 Pedrie Wannenburg.
Replacements: 16 Jeremie Maurouard, 17 Laurent Delboulbès, 18 Horace Pungea , 19 Fabrice Metz, 20 Maurie Fa'asavalu, 21 Fabien Cibray, 22 Regis Lespinas, 23 Eamonn Sheridan.
Watch Ulster v Oyonnax live on Sky Sports 5 HD on Saturday from 12.45pm. Catch the match for £6.99 on NOW TV. No contract.