Forest Green Rovers midfielder Al Bangura has had exploratory surgery on an ongoing knee injury.
The 23-year-old joined the club in the summer but has been restricted to just 11 appearances - his last game coming in November against Southport.
It is not yet known how much longer he will spend on the sidelines.
"He's had MRI scans, operations - the lot. He's distraught as all he wants to do is play," Rovers manager Dave Hockaday told BBC Gloucestershire.
"Something is aggravating the knee. He played in the reserves and played well, then he trained and then the knee swelled up.
"It might just be a foreign body in there that needs to be taken out or it could be something more sinister."