They duly lost 3-0 but reaped the benefits five days later when their first-choice XI claimed a 2-0 triumph over relegation rivals Burnley.
With Wolves set to host Liverpool on Tuesday, McCarthy again rested his top performers against Palace.
But despite receiving widespread condemnation from many quarters for his actions last time out, the resolute Yorkshireman was emphatic when asked whether he had one eye on on Rafael Benitez's side, who have enjoyed a free weekend.
"Of course I did," he said.
"But I still think that team that played was (strong enough). If anybody had that team in the Championship they'd be thrilled.
"I had no hesitation in making the changes."
Asked whether any of the seven had played their way into his thoughts for midweek, McCarthy replied: "I thought Sam Vokes was excellent and I actually thought Andrew Surman played really well, he's a clever footballer.
"David Jones also had an excellent game, so make of that what you will."
Whether the raft of changes affected Wolves' rhythm is another matter, but they could consider themselves fortunate to still be in the competition after a below-par performance.
Their battling Championship opponents twice took the lead through Alan Lee and Darren Ambrose, only for Jones and Ronald Zubar to come to the hosts' rescue - the latter salvaging a draw six minutes from time.
Beforehand McCarthy insisted the competition was "definitely not a distraction" to the main target of Premier League survival.
And he kept his stance afterwards despite seeing the replay scheduled for Tuesday February 2 - replacing what was already a rearranged date for Wolves' trip to West Ham.
He said: "It (the trip to Upton Park) was called off in the first place, we should have actually had it played.
"It's a distraction to them as well I guess isn't it? In terms of they can't play their game.
"But we want to be in the FA Cup and we are - we've just got another game to play. There's point whinging about it."
Palace manager Neil Warnock knows all too well the effects of squad rotation yet he stood firmly behind McCarthy.
Warnock was in charge of Sheffield United when they were relegated from the Premier League in 2006/07 as fellow strugglers Fulham and West Ham controversially saw off weakened Liverpool and Manchester United sides.
But the Eagles boss said: "I think the seven changes could all get in our team.
"Good luck to Mick. You know what my thoughts are about weakened teams after what I went through with Fulham, Liverpool, Manchester United and West Ham.
"They can't pick on Wolves can they?
"Mick's doing a great job and they've got a great chance of staying in that league, make no mistake. He's not going to jeopardise that.
"I hope he gets a great result on Tuesday now and the lads who haven't played play really well for him."
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