Doncaster defender Wayne Thomas has suffered a fracture to his knee.
The former Burnley and Southampton man sustained the injury in training but manager Sean O`Driscoll is confident the injury is not as serious as first feared.
He said: "Wayne went back down to London and spoke to the surgeon who operated on his knee before and he has a small fracture.
"It`s quite unusual but it explains why the knee had swollen so much.
"The surgeon is pondering what we can and can`t do. It may be something that we can just leave but there is no pre-determined diagnosis for it."