Colchester winger Ashley Vincent faces surgery on his ankle and could be out for up to two months.
The 24-year-old suffered the injury against Swindon Town in September and, although he briefly returned to training, now needs to go under the knife.
"We've discovered a floating bone in Ashley's ankle," Us manager Adrian
Boothroyd told the club's official website.
"While we could leave it alone and hope the problem settles on its own, we have decided with Ashley to have the operation done and get the problem out of the way.
"Ashley will go for the operation and, six to eight weeks down the line, it will be like having a brand new player in the squad."
Vincent has started seven games for Colchester so far this season, finding the net against Yeovil and Swindon.