Colchester have been dealt a blow with the news that combative midfielder John-Joe O'Toole faces up to nine months on the sidelines.
The 21-year-old had to be stretchered off in the 1-0 defeat at fellow League One high-fliers Charlton on Tuesday.
A scan has now confirmed ruptured cruciate ligaments and he will have knee surgery as soon as the swelling subsides.
Colchester boss Aidy Boothroyd said: "It's a blow for him and a blow for us.
"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."
The surgery will be the same procedure which team-mate Morten Knudsen undergoes on Thursday and Boothroyd says the pair will work side by side as they come back.
The Colchester boss added such a long rehabilitation will test O'Toole's mental strength but will ultimately make him stronger when he returns.
He told the club's official website: "John-Joe is already as tough as it goes but this will make him stronger as a person and a player.
"He will be working side by side with Morten and (first team physio) Tony Flynn and they'll be doing all they can to be back in action as soon as possible."