Five players - Johne Murphy, Doug Howlett, Barnes, Wian du Preez and O'Mahony - retain their places in the starting XV from the Ospreys game while James Coughlan missed that Ospreys clash through injury.
The selection reflects a certain urgency to get the RWC players back into action as coach Tony McGahan explained that Munster "need to hit the ground running."
"I think you'll have seen South African, English and other countries players come back and play as soon as they were out of the quarter finals. The Irish players had two weeks rest. We're already at least a week and a bit behind so we need to look at all the possibilities and people who are going to be best for us short term and long term in this 4 week block that we have."
Munster (v Aironi Rugby) RaboDirect PRO12 League, Friday (8.30pm) Musgrave Park.
J Murphy; D Howlett, W Chambers, D Barnes, K Earls; R O'Gara, C Murray; W du Preez, D Varley, BJ Botha; D Ryan, P O'Connell capt ; D Leamy, P O'Mahony, J Coughlan. Replacements: D Fogarty, M Horan, J Hayes, D O'Callaghan, N Ronan, T O'Leary, S Deasy, L Mafi.
(Not considered due to injury. David Wallace, Troy Smith, Felix Jones, Jerry Flannery, Peter Borlase, Darragh Hurley, Mike Sherry, Ian Keatley).