"Matty is going to be out a few weeks with that," Russ Wilcox told the club's official site.
"It's not a good injury and it's very swollen around his ankle. We think it's ligaments. He's had an X-ray and there's no break in there, which is great news.
"It's probably going to be four to six weeks. It's a bit blow for Matty. Hopefully we can get him back as soon as we possibly can."