Whyteleafe defender Tommy Smith faces a lengthy spell on the treatment table after picking up a freak injury on Tuesday night in the Surrey Senior Cup 5-2 defeat to Sutton United.
Leafe manager Steve Griffin said that, with only five minutes to go, Smith slid to clear a cross for a corner, caught his studs in the turf and went over awkwardly - severely damaging ligaments in his knee.
At first it was feared the promising 17-year-old had broken his leg, but tests revealed there was no fracture.
However, Smith is facing the Christmas holidays wearing a cast, and Griffin said only time will tell when he can return.
"Although it sounds worse, sometimes a break can be better, because it can heal with in seven or eight weeks," he said.
"But with ligament damage you never really know, and worst case scenario Tommy could be out for up to a year."
He added: "It was inocuous really. He cleared a cross and stayed down, and when he continued to say down, you begin to realise something is not right.
"He's a young lad, and is playing at a level of football higher than most his age. He was one of the better players on the night so it a shame for him.
"But we won't know how serious the damage is until it has calmed down."
Whyteleafe host Beckenham on Boxing Day in the Kent League Premier Division.