With Wolves' Premier League survival having been assured last month, their last two games of the season have been pressure free.
McCarthy admits that, after a virtual season long-battle to try to retain their Premier League status, not having any pressure is something new for the former Sunderland boss.
He said: "I know there are points and prize money at stake but it is not quite the same compared to that heart-wrenching, stomach-churning feel to a game.
I think that is natural.
"I have mixed emotions about it.
There is a real sense of pride and satisfaction about what we have achieved and the amount of people who keep telling me what a great achievement it is has been nice.
"But it hasn't really sunk in. I had a really strange feeling when it happened. It was almost an anti-climax that that gut wrenching, heart pounding feeling had gone. I am glad it has now and I am glad I don't have that for Sunday, I really am.
"Staying in the Premier League is a bigger achievement than winning the Championship.
"It just doesn't feel like it, celebrating 17th, 16th, 15th, 14th spot wherever we end up.
"Last season was wound up to a crescendo of winning the Championship and it is almost feels like you have wound down to staying in the league which seems barmy when it is a bigger achievement. But I can't help that.
"I am thrilled and delighted with it but it is still a strange thing."
After their survival had been assured Wolves lost 3-1 at Portsmouth last weekend - only their second defeat in nine games - and McCarthy added: "I think we have been so wound up to when we were safe that it is hard to get that back again.
"You always want to win the game but when that pressure is not there, there is something missing."
A win could see Wolves finish 14th while victory for Steve Bruce's Sunderland would give them a chance of securing 10th.
There is a certain taste of revenge to the game for Wolves as they were beaten 5-2 at the Stadium of Light last September - a result that McCarthy still describes as "ridiculous".
He added: "Sunderland can finish 10th so that is a something for them to play for. It looked like they were going to do it comfortably when they started.
"We lost 5-2 up there but anyone who saw that game will know it was the most ridiculous result ever. When we got back to 2-2 they were hanging on and after a great strike by Kenwyne Jones it all went wrong for us.
"They were scoring goals then and it looked like they were going to have a great season.
"But they went through a lean spell and have come back again and if they finish 10th then Steve will be delighted with that.
"At times, Steve was starting to look as flustered as I was on the touchline.
It is difficult when you get into that rut and can't win enough games.
"But they have come out of it again and if they finish 10th it will be a real achievement for them. They are a real solid team and they have got some good players."