Ferguson finally joined the Glasgow outfit training on Monday, 10 weeks after signing a loan deal from Newcastle United.
McCall, who will welcome 23-year old Ferguson back from a knee injury, said: "Hopefully Shane might play a part in the back end of the season but he won't be involved in the short-term because he needs games.
"He's been out for five months and has trained for the past two weeks, but the one good thing about him is his mental state.
"He trained on Monday and, having spoken to him, I was really impressed. He wants to get straight into it. If you've been out that long you're going to need four to six weeks to get back on track.
"He certainly won't be ready in the next couple of weeks but he did a lot of hard work yesterday and today.
"He's a naturally fit lad but when you've been out that long it's not just the physical aspect, it's the mental aspect, and he seems really focused. So that was pleasing."
'Gers currently sit third on Scotland's second tier with four league matches remaining.