The Israel international was out for four months with ankle ligament trouble after a tackle by the 35-year-old stopper during an Old Firm game in December 2011.
And according to the Israeli newspaper, Haaretz, Kayal 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."
However, speaking at the club's Murray Park training ground ahead of Sunday's Ramsdens Cup final against Raith Rovers at Easter Road, the Ibrox manager 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 Old Firm 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 Old Firm 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."
McCoist has plenty of injury worries for the trip to Leith.
The former Rangers striker is hopeful that midfielder Nicky Law will recover from a back injury.
However, midfielder Ian Black (foot) and forwards David Templeton (groin), Andy Little (thigh) and Jon Daly (hamstring) are all doubts.
"I am more hopeful about Nicky Law, more than anyone else," said McCoist.
"There are still big doubts over Templeton and Little, they are very doubtful.
"We are going to let big Jon and wee Blacky go until the end of the week and we will see how they get on."
Midfielder Lewis Macleod is still suffering from a viral issue and awaiting test results being analysed.
McCoist said: "The doctor is in the process of sending results down south so until we get the opinion back I can't say any more.
"He has had a very uncommon reaction to a common virus which has affected lot of muscles in his body and some of the muscles around his heart.
"That said, he is in a better place than where he was three or four weeks ago when he stopped playing.
"There has been an improvement which is a real plus. It is not a complete shutdown, he has been keeping himself going in the gym, so we are obviously very hopeful."