If you're not good enough then that's it. If he didn't cut it, and at the end of the day I don't think he did, then it is time for him to move on and someone else like Carswell or Hetherington to take their shot at a first team spot.
Law, Daley, Humphrey, Lasley, Murphy, Ojamaa, Hetherington, Ramsden and Carswell could all do a shift, at some point, in a four or five man midfield. No reason why a good number of them couldn't play in the middle as well.