Cowell has headed the U.S. talent show's panel since its inception in 2002, but announced last month (Jan10) that he would be quitting the programme when his contract expires in May (10).
His departure has prompted speculation over who will take his place on the show, with recent guest judges Victoria Beckham and Katy Perry among the rumoured replacements.
Foxx has previously confessed he's a fan of the singing competition - but insists he's not joining Ellen DeGeneres, Kara DioGuardi and Randy Jackson as the new fourth judge.
He tells E! News, "I would love to do it but I don't think I would be able to do it. I don't think I could fill Simon's shoes, but I would give it another perspective...what I want is for the kids to go from being contest participants to artists and that's where I would come in."