The other change up front sees Wian du Preez replace the injured Julien Brugnaut (groin) while McGahan's bench has a decidedly youthful look to it drawn as it is from either Academy or Development players, the only exception being Tom Gleeson who sits out the start behind Lifeimi Mafi.
With three of the regular Os not available by international dictat, Paul Warwick slips into the number 10 jersey while the fourth O, Mick O'Driscoll will captain the side.
Munster, although buoyed by their bonus point win over Connacht last time out will need no reminding of the type of challenge that they face on Saturday.
"It's easily one of the toughest games of any season." says skipper Mick O'Driscoll. "They have a great home record and besides that, last weekend without key players, they gave a full strength Leinster one helluva game. So yes, it's going to be very difficult to get anything out of this one. Always is in Ravenhill, but these are the sort of games you want to play in and I'd be happy with our form going into it."
Munster. Denis Hurley; Doug Howlett, Lifeimi Mafi, Jean de Villiers, Ian Dowling; P Warwick, P Stringer; W du Preez, D Varley,T Buckley; M O'Driscoll, D Ryan; B Holland, N Ronan, J Coughlan. Replacements: M Sherry, S Archer, P O'Mahony, T O'Donnell, D Williams, S Deasy, T Gleeson.