Michael Chopra's deflected shot gave Ipswich a shock half-time lead before goals from Darren Bent - against his former club - and Andreas Weimann turned the game in Villa's favour.
McCarthy said: "When I came the remit was to stay up and that has not changed.
"Maybe a replay would have got in the way but you don't like to lose and, when we were 2-1 down in the final minute, I would have taken a replay.
"I'm stewing about the goal we conceded just after half-time to bring them level.
"It changed the course of the game and, if you give them opportunities, they have the quality to make it count.
"But I was pleased with our performance as a whole."
McCarthy confirmed he would like to sign QPR striker DJ Campbell on a permanent basis after his recent loan spell at Portman Road.
He added: "I spoke to him [on Friday night] and told him I'd like to sign him. We will have to see what happens."