McCall said: "Chris came to see me and apologised for not being available, but injuries happen.
"He's just got to concentrate on getting right. People forget what happened in September or October, they only remember the last month or so of the season.
"Chris might turn out to be our most important player. That's what he has got to focus on."
McCall added: "Of course he's frustrated because he's desperate to do well for us, but he's been out a long time and will need a month of football before he is back."