Leinster will travel will a full deck behind the scrum and missing only the blockbusting Sean O'Brien up front. As for the French champions, they may be very strong at home but they will have to do without the services of a key quartet in Rory Kockott, Antonie Classen, Mathieu Bonello and Romain Martial.
Castres were stubborn opponents in Dublin, where they fell 17-9 a week after beating Northampton Saints at home. That opening win seemed to have prepared the ground for a possible return to the quarter-finals after a 12 year lapse, but the signs are no longer as encouraging.
Leinster have won 12 and drawn one of their last 15 away games in the Heineken Cup and are seasoned campaigners and travellers in the tournament. There won't be anything the likes of Gordon D'Arcy, who will play his 96th game in the Heineken Cup, centre partner Brian O'Driscoll, Leo Cullen and skipper Jamie Heaslip won't have seen.
- All three previous meetings between these sides have been won by the home team (Leinster W2).
- Leinster have a tackling success rate of 91% this season, a joint-high in the tournament along with Gloucester.
- Castres have the worst ball retention rate at the ruck this season (90%).
- Leinster have lost just one of their last four away games in France (W2 D1).