Castres travel to Bayonne on Thursday looking to bounce back from elimination from the Heineken Cup and stay in touch with the Top 14 leaders.
CO currently lie fourth in the standings, six points behind third-placed Toulouse as they seek to secure a home play-off in May.
For Bayonne, who lie eleventh, victory will put some breathing room between the Basques and the relegation zone.
Both teams have been knocked out of their European competitions after Bayonne failed to get out of their Amlin Challenge Cup pool.
Castres have won twice in their last eight visits to Bayonne (in 2009 and 2005) and will be chasing their fourth win on the road this season.
The hosts however seem to be on an upward curve having won their last three Top 14 home games.
Bayonne are without former France international full-back/wing CÚdric Heymans, who is struggling with a knee injury. Ex-All Black wing Joe Rokocoko continues his conversion into a centre as he starts in the number 13 jersey. Wales scrum-half Mike Phillips starts inside South African pivot Jacques-Louis Potgeiter.
For Castres, their all-time record points-scorer Romain Teullet is sidelined with a wrist injury so Remi Tales starts at fly-half with Rory Kockott set to do the place kicking.
Bayonne: 15 Scott Spedding, 14 Sam Gerber, 13 Joe Rokocoko, 12 Gabiriele Lovobalavu, 11 Marvin O'Connor, 10 Jacques-Louis Potgeiter, 9 Mike Phillips, 8 Dwayne Haare, 7 Julien Puricelli, 6 Jean Joseph Marmouyet, 5 Mark David Chisholm, 4 Dewald Senekal, 3 Nemiah Tialata, 2 David Roumieu, 1 Aretz Iguiniz.
Replacements: 16 Gregory Arganese, 17 Pierre Lafond, 18 Abdellatif Boutaty, 19 Marc Baget Rabarou, 20 Cedric Garcia, 21 Benjamin Boyet, 22 Thibault Lacroix, 23 Renaud Boyoud.
Castres: 15 Brice Dulin, 14 Romain Martial, 13 Romain Cabannes, 12 Remi Lamerat, 11 Marc Andreu, 10 Remi Tales, 9 Rory Kockott, 8 Antonie Claassen, 7 Yannick Caballero, 6 Jan de Bruin Bornman, 5 Iosefa Tekori, 4 Matthias Rolland, 3 Anton Peikrishvili, 2 Brice Mach, 1 Yannick Forestier.
Replacements: 16 Marc Antoine Rallier, 17 Michael Coetzee, 18 Christophe Samson, 19 Piula Faasalele, 20 Thierry Lacrampe, 21 Daniel Kirkpatrick, 22 Marcel Garvey, 23 Mihaita Lazar.
Previous result Castres won 31-10
Date: Thursday, 24 January
Venue: Stade Jean Dauger, Bayonne
Kick-off: 21.00 (20.00 GMT)
Referee: Pascal GaŘzere