Denis Hurley was expected to make a return to action but tweaked a hamstring in training yesterday and that means a start for youngster Danny Barnes on one wing with another young gun, Simon Zebo on the other.
Commenting on the changes, McGahan said, "After three challenging weeks previous to this away trip to Scarlet's, a rotation of the playing group allows us to rest many of the starters coming into a busy and competitive period.
"It also allows for competition within the squad for opportunities across the 23 and there is no better place or opposition for players to test themselves than Scarlets in their home ground."
Munster: P Warwick; S Zebo, J Murphy, L Mafi, D Barnes; D Cusack, P Stringer; M Horan, M Sherry, S Archer; D Ryan, M O'Driscoll T O'Donnell, N Ronan, D Leamy capt. Replacements: D Fogarty, D Hurley, J Hayes, A Quinlan, P Butler, D Williams, S Tuitupou, S Deasy.