John-Joe O'Toole is likely to be out for up to nine months after it was confirmed that he has ruptured his cruciate ligament.
The young Colchester United midfielder injured his knee in the first half of his side's 1-0 defeat at Charlton Athletic on Tuesday night.
He will undergo an operation in the next two weeks and will then begin his long rehabilitation process.
U's manager Aidy Boothroyd said: "It's really, really disappointing and it's the last thing anyone wanted.
"But it's part and parcel of football and we have to make sure that when he comes back, we're playing in a different league next season."
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