Only central defender and acting skipper Christophe Berra was retained from the side which drew at Tottenham and a crowd of barely 10,000 greeted the replay reversal with boos at the final whistle.
But McCarthy felt the side he fielded was still good enough to progress, and said: "I know the questions will be asked about the team and, if people want to point the finger at me, then so be it. But I thought that team against Birmingham should be good enough to win at home."
He added: "Every single one of them were Premier League players. I had four players that were definitely injured. I was also never going to play Steven Fletcher or Wayne Hennessey, and I made the other decisions.
"If I picked the wrong team, then maybe one of the players who came in should be telling me, because they all want to play and are ready to play.
"They are all good enough and good footballers in the Premier League.
"Just because players aren't involved sometimes, it doesn't mean that I forget them and I'm not that shallow that I only consider the eleven.
"It is an opportunity when they get a chance to play but we weren't as good as we should have been, that's for sure.
"I know they can all do it but individually and maybe collectively they maybe didn't do as well as they could have done.
"But they've to be in my thinking. We've got 17 games left and there is no point discounting anybody because they haven't played as well as they can."