With a full-strength backline looking to fire, there's plenty of potential in attack for the Scarlets to push a high-scoring game and with Stephen Jones and Rhys Priestland both starting the Scarlets have plenty of options and experience.
A potent attacking backs division includes Jones at outside half with Priestland at full-back, Jonathan Davies and Scott Williams in a centre partnership and Liam Williams and George North on the wings with exciting young scrum-half Rhodri Williams at nine.
The Scarlets took the spoils from the French side at home in November. Head of Rugby Nigel Davies said the frustration of last week was well behind the team and it was all about bringing everything together against the French to back up the big performances and commitment his side had shown throughout their Heineken Cup campaign.
Davies said: "We know how close we have come to results against some of the best sides in Europe including Munster and the effort and mentality that went into beating Northampton at their home - so this is about making our statement on this game and finishing the pool stages with our heads up.
"We had expectations of ourselves in this tournament and it is very disappointing for us not to have got to the knock-out stages but that itself shows some how far we have come in a short amount of time. In the three games we've narrowly lost the margins have been very small and the result and hurt of last weekend will drive us on."
Davies added: "This team knows they can go toe-to-toe with anybody and for this weekend we just have to go out there and show that. "It won't be easy, winning out in France is a big challenge - but if we create the same amount of opportunities as we did against Northampton and look to be more clinical, then we have a good chance of achieving what we need to."
Scarlets team against Castres Olympique Saturday 21st January 2012:
15 Rhys Priestland, 14 George North, 13 Scott Williams, 12 Jon Davies, 11 Liam Williams, 10 Stephen Jones (capt), 9 Rhodri Williams, 1 Phil John, 2 Ken Owens, 3 Peter Edwards, 4 Lou Reed, 5 Dominic Day 6 Aaron Shingler, 7 Johnathan Edwards, 8 Matt Gilbert.
Replacements: 16 Emyr Phillips, 17 Iestyn Thomas, 18 Rhodri Jones, 19 Sione Timani, 20 Richie Pugh, 21 Gareth Davies, 22 Gareth Maule, 23 Viliame Iongi.