Pierre Bernard starts at full-back for Castres in one of eight changes from the side that took on Northampton.
Seremaia Bai returns at centre, with Rémi Tales coming in at 10 to replace Daniel Kirkpatrick.
A new back-row sees Pedrie Wannenburg, Piula Faasalele and Mathieu Babillot all start, with Matthias Rolland coming into the second-row to partner Christophe Samson. Hooker Marc-Antoine Rallier is the final change for Mathieu Bonello.
Castres will want to do themselves justice after the manner of their 41-17 defeat they suffered to the Irish province in the opening game of this Pool back at Ravenhill back in October.
The French side suffered a narrow 18-12 defeat to Northampton Saints in their last game in the Pool and cannot qualify for the quarter-finals but they could deny Ulster a home draw in the last eight.
They will be confident that they can make life difficult for Ulster at their formidable home ground of Stade Pierre Antoine, where the Belfast side have never played before.
Meanwhile, Ireland winger Craig Gilroy starts at full-back for Ulster on their trip to France, with Michael Allen taking his free place on the left wing.
Ruan Pienaar is moved to fly-half with Paddy Jackson dropping to the bench, Paul Marshall getting the nod at scrum-half after being named in the expanded Ireland squad for the Six Nations earlier this week.
Roger Wilson replaces the injured Nick Williams at number eight whilst Neil McComb comes in for Iain Henderson at lock. The front-row remains unchanged.
The Irish province, who are also top of the PRO12 table, have reached their third successive Heineken Cup quarter-final and were beaten finalists in last season's tournament.
Ulster are the only Irish province to have qualified for the quarter-finals with a game to play, with both Leinster and Munster still needing victories in their final games to have any chance of qualification.
The Belfast side, who won the tournament back in 1999 recorded a hard-fought 23-6 victory over Glasgow Warriors at Ravenhill in the last round and will be under no illusions of what faces them in France.
Castres: 15 Pierre Bernard, 14 Max Evans, 13 Seremaia Bai 12 Rémi Lamerat, 11 Marcel Garvey, 10 Rémi Tales, 9 Rory Kockott, 8 Pedrie Wannenburg, 7 Piula Faasalele, 6 Mathieu Babillot, 5 Christophe Samson, 4 Matthias Rolland, 3 Anton Peikrishvili, 2 Marc-Antoine Rallier, 1 Yannick Forestier.
Replacements: 16 Brice Mach, 17 Saimone Taumoepeau, 18 Mihaïta Lazar, 19 Iosefa Tekori, 20 Thierry Lacrampe, 21 Jannie Bornman, 22 Paul Bonnefond, 23 Marc Andreu.
Ulster: 15 Craig Gilroy, 14 Andrew Trimble, 13 Darren Cave, 12 Paddy Wallace, 11 Michael Allen, 10 Ruan Pienaar, 9 Paul Marshall, 8 Roger Wilson, 7 Chris Henry (c), 6 Robbie Diack, 5 Neil McComb, 4 Louis Stevenson, 3 John Afoa, 2 Rory Best, 1 Tom Court.
Replacements: 16 Rob Herring, 17 Calum Black, 18 Declan Fitzpatrick, 19 Iain Henderson, 20 Mike McComish, 21 Michael Heaney, 22 Paddy Jackson, 23 Chris Cochrane.
Date: Saturday, 19 January
Venue: Stade Pierre Antoine
Kick-off: 14:35 (13:35 GMT)
Referee: Nigel Owens (Wales)
Assistant referees: Sean Brickell Jon Mason (Wales)
Television match official: Derek Bevan (Wales)