Wolves lost 3-0 at Old Trafford on Tuesday and McCarthy was widely criticised and asked by the Premier League to explain why he had made 10 changes to the team that had beaten Tottenham Hotspur the previous Saturday.
Arsenal manager Arsene Wenger added his voice to the debate by saying he now only had 37 games in which to compete with United, instead of 38, because of McCarthy's actions.
Ferguson made light of that on Friday, with a joke at Wenger's expense.
"I wish we were playing him over two games...the last two," he told reporters.
"I think Mick McCarthy did the right thing for Wolves Football Club," he added.
"We looked at their performance at Tottenham and we thought they would make six changes, with the amount of running they had to do on the Saturday against Tottenham and then travelling up to Manchester on the Tuesday.
"So we weren't far wrong. Of course, we didn't expect 10 changes but there wasn't any discernible difference between the Wolves team that could have played and the team that did play on Tuesday."
Ferguson said as many as five clubs could be in contention for the title right to the finish after United lost 1-0 to Aston Villa at Old Trafford on Saturday.
"With the form of Aston Villa now, you have to look over your shoulder and think, wait a minute," he said.
"They have a lot of experience in the right quarters, their back four was terrific last week. Then Tottenham got a big win during the week so they are now challenging that top group," added Ferguson.
"The history of the league does point, over the years, to it becoming a two-horse race but it does change.
"From an interest point of view, a spectator's point of view, you hope four or five teams will come through over the last month of the season. It would be fantastic and it is capable of being like that."
