Carroll has not played this season due to a foot problem after making his loan move from Liverpool permanent over the summer.
The England international recently returned to light training and is now stepping up his recovery with Sam Allardyce's side.
McDonald said: "Andy did a training session yesterday (Sunday) which is very encouraging.
"It's early stages but is a work in progress with him. Work one day on the training pitch, massage and rehab the next day and let's see how it goes from there.
"It's a positive he is in training but it is a slow process.
"When you are out for seven months I don't think you can rush anybody back.
"Obviously, we are all desperate for him to come back and get into the team as quickly as possible but we have to be sensible and he is getting closer."
Ahead of Wednesday's trip to Craven Cottage to face fellow strugglers Fulham, McDonald confirmed that James Collins, Winston Reid and James Tomkins are all likely absentees.
He said: "It looks as though all three (Collins, Reid and Tomkins) are not going to be fit for the Fulham game.
"We will assess them ahead of the Forest game (FA Cup) but it is more likely they will be involved in the Cardiff game (January 11)."
And regarding January's transfer window, he added: "We have a few defensive problems and with the window coming up Sam (Allardyce) is working non-stop.
"We need some reinforcements to boost the players we have here so he is working behind the scenes with everyone else. His phone is going non-stop.
"We have three main centre-halves injured at the moment. We are aiming to improve and the two main places are in defence and in attack."