From an interview in the Detroit News:
Q. You've referenced often how huge the Ohio State rivalry is. Where do you stand on the Michigan State rivalry?
A. I think it really is the same in a lot of ways. It didn't happen very much when I was here as an assistant, but it's not much fun being on the wrong end of that game.
That's the great thing about Michigan. We have Notre Dame, that's a heckuva rivalry. The Michigan State game, that's an unbelievable rivalry. And on a national scale, Michigan and Ohio, big time.
Q. You always say "Ohio" instead of "Ohio State."
A. Yeah.
Q. How come?
A. (Smiles.) I don't know.