McCoist was reacting to Celtic midfielder Beram Kayal's claim that the former Motherwell and Wigan defender meant to hurt him during a match between the sides in December 2011.
Kayal, who spent four months on the sidelines after the tackle, said: "The injury didn't look that bad but I believe he did it on purpose. That player is not the cleanest in the world."
But McCoist said: "Anybody who knows Lee, knows he is not a dirty player. I don't think he is a dirty player at all. I can't even remember the tackle or the incident.
"I defend my player and my skipper against any comments like that. With the greatest respect to Kayal, I would have the Old Firm games down as quite tame in comparison to some of the previous games.
"I am not sure he would have enjoyed playing with Bertie Auld (former Celtic midfielder) and John Greig (former Rangers captain) in some of those games, that would maybe have been a wee eye opener for him.
"But as I say, I would need to defend my player. He is not a dirty player at all and we are delighted with the skipper, the way he handles himself on and off the park."