Munster's starting back-line remains the same with captain Doug Howlett leading the side out on the occasion of his 100th competitive appearance for the province.
Ronan picked up a slight groin injury in training on Thursday, while Horan continues to recover from a cut under the eye that he received in an Ulster Bank League outing for Shannon.
That means a second start in an interprovincial derby this season for young prop David Kilcoyne, who also lined out against Ulster last month. The 23-year-old comes in for Wian du Preez who drops to the replacements bench.
Elsewhere, Ireland internationals Donnacha Ryan and Peter O'Mahony return to the starting line-up for the first time this season.
David O'Calllaghan also resumes at blindside flanker, a position he impressed in during three of Munster's recent games against Benetton Treviso, Ulster and the Newport Gwent Dragons.
MUNSTER (v Leinster): Denis Hurley; Doug Howlett (capt, Keith Earls, Casey Laulala, Simon Zebo; Ronan O'Gara, Conorr Murray; David Kilcoyne, Mike Sherry, BJ Botha, Donncha O'Callaghan, Donnacha Ryan, David O'Callaghan, Sean Dougall, Peter O'Mahony.
Replacements: Damien Varley, Wian du Preez, Stephen Archer, Billy Holland, Paddy Butler, Duncan Williams, Ian Keatley, James Downey.