O'Mahony's was a blood injury, while O'Leary shipped a heavy tackle and considering the type of schedule facing Munster, the management took the prudent step of replacing him immediately.
Meanwhile, Jerry Flannery had a positive diagnosis following his visit to specialist in Germany last week although as yet there is no definite timeframe for a return to full training.
David Wallace, Felix Jones, Mike Sherry, Peter Borlase and Troy Smith are the other players who remain unavailable through injury.
Next Friday's match will be just the second of Munster's season for many of the players including captain Paul O'Connell, who looked particularly sharp in the victory over the Italians.
"I enjoyed the game. Our scrum was excellent against Aironi. On nights like that a strong scrum is of massive importance," explained O'Connell following Monday's training session.
"All things considered I think it was a good performance. We really need to start building relationships with each other again, and getting used to playing with each other.
"I've rarely if ever played with Peter (O'Mahony), obviously never played with BJ (Botha). That was Will Chambers' first game with the senior side. First time Danny Barnes played at inside centre. There are a lot of combinations there that are new.
"So we really need to get to know each other quickly. To get all the guys off the bench and finish the game in their half pummelling them was good for us."
And looking forward to the Leinster game, the experienced lock added: "It's probably the highest level you can go in Europe at the moment - Leinster, with their record, with the playing squad they have.
"It's going to be a massive step up for us and again the following week in our Heineken Cup opener against Northampton.
"So, it's really good preparation for us but we really need to learn fast and hit the ground running next weekend."