Discussing the potential appointment of McCarthy, Stewart had only positive things to say about the 53-year-old following their stint together at Sunderland.
"Mick is a top bloke, a top manager and Ipswich would benefit from having him. I can't speak highly enough of him. I have played under lots of managers and have learnt things from all of them," Stewart told the East Anglian Daily Times.
"Mick is the best. I have huge admiration for him and he has a way about him that commands respect. His man-management skills are excellent. He is honest and straight-talking and that is why people think he is a disciplinarian.
"He has no airs and graces and I think most players just want to hear the truth."
It has been speculated that McCarthy will be confirmed as Ipswich's new manager tomorrow.