Second-half goals from Andy Carroll, Craig Bellamy and Dirk Kuyt at Molineux completed a memorable seven days for the Reds after their Carling Cup and FA Cup triumphs over the two Manchester clubs.
But Wolves have now gone nine league games without a win - a run from which they have collected just four points - and there were boos at the final whistle on Tuesday night.
McCarthy said: "After the last home game (against Aston Villa), there were huge rumours that I wouldn't be here.
"I can't imagine there will be any less after this game. We will see. I can hear what the fans are saying and I fully understand it.
"It was an unacceptable performance from us in the second half and watching that was unacceptable for me or anybody else.
"That's as bad a performance as we've had here or away. Fans pay good money to come and watch and they expect better and I understand that.
"If I had been watching, I'd have probably responded like that as well."
McCarthy added: "The lads are hurting, there are none of them that have come and not tried.
"But once we've conceded, we've gone on to be beaten by a considerably better side who have just beaten Manchester City and Manchester United.
"If you give them goals then it becomes hard work but I understand people's reactions."
The only consolation for McCarthy was the signing of Tottenham defender Sebastien Bassong on loan until the end of the season shortly before the transfer window closed.
