Town boss Joe Royle says he is unlikely to bring in a loan defender as cover for the suspended Richard Naylor at Derby on Saturday. Naylor and midfielder Chris Bart-Williams are both suspended after reaching five bookings.
Royle said: "I haven't totally ruled out that option. But Richard is only out for one game, Drissa Diallo and Chris Makin are on their way back and there's also John close to full fitness. It is not an ideal situation.
"It would be a big decision to bring in a loan player - a really big call - and it might effectively be for one game only."
McGreal will get a run-out in the reserves on Wednesday and says he is keen to get involved in the first team again: "I'm hoping I can get a full 90 minutes under my belt against Forest and then go straight into the first team squad.
"I imagined it would take a lot longer than this to get back, but the situation we are in with injuries and suspensions has given me a chance.
"If all goes well I'll definitely be ready at the weekend. It's a chance and I mean to take it."