However McGahan did reveal that injured trio Paul O'Connell, Donnacha Ryan and Conor Murray remain in contention for the clash against Brian McLaughlin's side.
McGahan said: "We are disappointed with the performance. We were second best pretty much in all areas.
"No one is ruled out (of the Ulster game) at this stage. We hope to have them all for selection from Tuesday to see how they train and get through. We would be hopeful.
"Paul O'Connell, Donnacha Ryan and Conor Murray have a fair chance of getting through at this stage.
"Denis Hurley trained most of the week. He had a bad 'cork' injury. We felt it prudent not to put him in a position to play this week.
"David Wallace was certainly around the same level. He has been making a slow comeback with 20 minutes of game time followed by two 40 minutes. We are monitoring his progress.
"As for the game with Leinster, we are not too bad. Keith Earls has a sore rib. BJ Botha has a sore rib too. Dave O'Callaghan picked up a knock, but apart from that it doesn't seem too bad."
Guinness PRO12 Munster News
63x46.png){kind=logo}