Rangers will have midfielder Lee McCulloch available to face Celtic on Wednesday after the club appealed his red card at St Mirren on Saturday.
The experienced McCulloch was dismissed for aiming an elbow at Graham Carey in Rangers' 2-1 defeat in Paisley.
The Scottish Football Association will not hear his appeal until 5 January at the earliest, so he can face former club Motherwell at Ibrox on 2 January.
Dorin Goian, though, is suspended for the Old Firm derby at Celtic Park.
The match against the Buddies had started well for the Scottish Premier League leaders when Lee Wallace opened his goalscoring account for the club after 11 minutes.
But McCulloch was sent off by referee Steven McLean when jostling in the penalty area at a free kick and St Mirren hit back with goals from Aaron Mooy and Paul McGowan late in the first half.
And McCoist thought the red card was pivotal to the outcome of the match.
"There is no doubt it changed the game," he said. "The ball actually went into the back of the net as well, which a lot of people maybe forget, so it might have been 2-0.
"I've seen it once and I would have to say it was extremely harsh.
"I've had a good chat with Lee McCulloch and he assures me there was no malice at all and he was just trying to fend the boy off. The boy actually had an arm around his waist.
"I'm a wee bit disappointed with how the boy went down to be honest with you and no physio came on to my knowledge.
"It changed the game, there is no doubt about it, and we are disappointed with it."
Goian was booked for a tug on Gary Teale's jersey and earnt a second caution for doing the same thing to Kenny McLean late in the game.
Asked if he was annoyed by that red card, McCoist said: "Yes I am, but that's just the referee to be fair. The referee will tell you technically he is right and that's it.
"There is nothing I can say on it any more other than he probably could have stayed on the park."