The 26-year old French-Tunisian was sent off during the weekend's 2-1 win over Brechin City for two bookable offences - the second arriving when he kicked the ball at an opponent after the play had ceased.
In the wake of that red card, McCoist has likened Mohsni to former 'Gers firebrand Madjid Bougherra while telling him to improve his disciplinary record so the team does not suffer.
"I was very angry and disappointed on Saturday. Bilel knew that and the sending-off was silly and needless. It put us under a little bit of pressure," McCoist said.
"Bilel is like Madjid Bougherra was in many ways. They're both really passionate about their football and they react differently when they think an injustice has taken place.
"There was certainly no injustice in the sending-off, though. We just have to direct Bilel's passion and his natural aggression and sometimes he needs to take a step back.
"If that means counting to 10, he needs to count to 10. As I've said to him today, he's no use to us if he's suspended."
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