The Scottish champions had hoped to strengthen their grasp on top spot in the Clydesdale Bank Premier League ahead of the trip to Parkhead but instead slumped to a 2-1 defeat at St Mirren on Christmas Eve.
Rangers could also be without Lee McCulloch and Dorin Goian on Wednesday night, after both players were shown red cards against Saints.
However, McCoist is likely to appeal McCulloch’s dismissal for violent conduct and, with an appeal hearing unlikely to take place before Thursday, the midfielder could still feature in the derby.
McCoist insists there is no chance of the rest of his players dwelling on what was a miserable day all round for Rangers ahead of the highly-anticipated meeting with the Hoops.
He said: “I can assure you we will be ready for the game, I can guarantee you that.
“It’s going to be a tough game but we will be ready and the players won’t need lifted for that one because it’s a big, big game.”