Sale captain Jason Robinson:
"It's a great result for us. Castres are a very strong team - especially at home - and I think we showed great character in coming through and winning this game.
"I think it's our best win in Europe, but it's still early days for us.
"Our team's going to get better and although we're not going to get carried away, we're certainly going to enjoy this and look forward to next week."
Castres: R Teulet; L Milford, N Raffault, P Christophers, R Ropati; Y Delaigue, A Albouy; C Hoeft, R Vigneaux, K Meeuws (capt), K Ghezal, L Nallet, J Puricelli, P Volley, F Faure.
Replacements: D Roumieu, Y Forestier, J Castex, F Capo Ortega, G Taussac, F Tuilagi, M Barrau.
Sharks: D Larrechea; M Cueto, M Taylor, E Seveali'i, J Robinson (capt); C Hodgson, S Martens; A Sheridan, S Bruno, S Turner, C Jones, D Schofield, J White, M Lund, S Chabal.
Replacements: A Titterrell, B Stewart, I Fernandez Lobbe, N Bonner Evans, R Wigglesworth, V Courrent, R Todd.
Referee: Alan Lewis (Ireland).