Mike Ross and Brian O'Driscoll out for Leinster as Munster ring changes
Munster make five changes for crucial Gloucester clash
Both Brian O'Driscoll and Mike Ross will miss out through injury for Leinster's clash with Castres at the RDS tomorrow.
Munster have also made a number of changes for their must-win clash with Gloucester. The one change to the Reds back-line sees Johne Murphy take the place of the injured Simon Zebo on the wing and in the pack Penney introduces Damien Varley, BJ Botha, Donncha O’Callaghan and captain Peter O’Mahony.
Meanwhile, Ireland duo Fergus McFadden and Kevin McLaughlin will both make their landmark 100th appearances for the Leinster province in Saturday's game.
This means that there is one change to the starting line up from the side that defeated the Ospreys last weekend with Martin Moore set to make his first Heineken Cup start after appearing as a replacement in Swansea last weekend in place of the injured Mike Ross (hamstring) who is close to regaining full fitness.
Former Leinster Under-20 captain Moore will start in the front row alongside Sean Cronin and Mike McCarthy in the pack.
Jamie Heaslip is captain once more on his 170th appearance. He is joined in the back-row by McLaughlin and last weekend's Heineken Man of the Match Sean O'Brien.
The backline is unchanged which means that Jimmy Gopperth, who gets the nod over Ian Madigan, will make his home European debut for the province alongside Brendan Macken (lining out for the 30th time in Leinster colours) who partners Gordon D'Arcy once more at centre.
Michael Bent has recovered from injury to take his place on the replacements bench alongside four other Ireland internationals.
Rob Kearney, Fergus McFadden, Brendan Macken, Gordon D'Arcy, Dave Kearney, Jimmy Gopperth, Isaac Boss, Cian Healy, Sean Cronin, Martin Moore, Devin Toner, Mike McCarthy, Kevin McLaughlin, Sean O'Brien, Jamie Heaslip captain.
Replacements: Aaron Dundon, Jack McGrath, Michael Bent, Quinn Roux, Rhys Ruddock, Eoin Reddan, Ian Madigan, Luke Fitzgerald
Felix Jones; Keith Earls, Casey Laulala, James Downey, Johne Murphy; Ian Keatley, Conor Murray; Dave Kilcoyne, Damien Varley, BJ Botha; Donncha O’Callaghan, Paul O’Connel; Donnacha Ryan, Niall Ronan, Peter O’Mahony Capt. Replacements: Mike Sherry, James Cronin, Stephen Archer, James Coughlan, CJ Stander, Cathal Sheridan, JJ Hanrahan, Denis Hurley.