McDonald doesn't expect McCarthy to be staying with the Latics for too long and sees the Ireland midfielder moving to a bigger stage.
He told The Herald: "James McCarthy was the youngest player to appear in our first team, when we were in the First Division," said McDonald. "He was 15. It is just as well we were not in the SPL then because he would have had to wait until he was 16.
"I am sure will be able to find other good young players but I would be cautious about saying we might find another James McCarthy because he has developed so much at Wigan. He will be a real top Premier League player. I saw him in pre-season and he's now 6ft 1in and has filled out. Wigan are convinced he will move one day to a top- four club in England. He will be a star.
"People thought I was conning them, but James has proved himself in the Premier League. If he was out there, then it is safe to assume that there are others who can be developed. Clubs are cutting back in their youth policies because of financial constraints but we will find players they do not keep, like we did with James McCarthy who had been at Celtic and Livingston, and James McArthur who had been at St Johnstone."