Isaac Boss will partner Jonathan Sexton when Leinster face ASM Clermont Auvergne in Sunday's Heineken Cup semi-final in the Stade Chaban-Delmas (3pm Irish time).
Gordon D'Arcy will take a familiar position alongside Brian O'Driscoll at centre with Luke Fitzgerald joining Isa Nacewa - who will make his 99th Leinster appearance - and Rob Kearney in the back three.
Twenty-four-year-old Clontarf prop Cian Healy, who makes his 94th Leinster career appearance and his 36th in Europe, starts in the front row alongside Richardt Strauss and Mike Ross.
Leo Cullen leads the team and partners All Black Brad Thorn at lock, with Shane Jennings joining fellow Ireland internationals Sean O'Brien and the returning Jamie Heaslip in the back row.
Leinster’s strong bench sees Reddan keeping company with the likes of Sean Cronin, Fergus McFadden and Kevin McLaughlin.
Leinster (v Clermont Auvergne): R Kearney; I Nacewa, B O’Driscoll, G D’Arcy, L Fitzgerald; J Sexton, I Boss; Cian Healy, R Strauss, M Ross; L Cullen (C), B Thorn; S O’Brien, S Jennings, J Heaslip.
Replacements: S Cronin, H van der Merwe, N White, D Toner, K McLaughlin, E Reddan, I Madigan, F McFadden.