The Blues midfielder limped off the St Andrews pitch 65 minutes into the game against the Dons with a recurrence of the hamstring injury that kept him out of Blues' last Premier League game at Chelsea last weekend.
"He's had a hamstring problem but he joined in training from Wednesday and wanted to throw his name in the frame for the game," said Blues coach Mark Bowen after the game.
"Full credit to him for that. He wants to play and train all the time and he's played the game and his hamstring has flared-up again.
"At this stage we don't know how bad it is going to be. We'll give it twenty-four hours to settle down but it could be a problem for us because this kind of injury tends to linger and if you don't get them exactly right they can drag on for a while."