The 20-year-old has been out of action since April with cruciate ligament damage.
McAllister said: “Fabian is doing fantastically well.
“He’s gone over to the United States to break his rehab up and he’s done some training with a specialist over there just to break up the routine.
“It’s been a long time out for Fabian and he’s having five or six days over there and then he will be back.
“Fingers crossed, he’ll be here in January.”
He added: “He is a talented boy, no doubt about that, an honest player and someone I admire.
“He loves to play and he loves training. He’s a bit frustrated at the moment but he is getting closer.
“This (break) has been a good chance for him to reflect and have a good look at the Premier League.”
