Colchester midfielder John-Joe O'Toole could be out for a substantial amount of time after picking up a knee injury against Charlton on Tuesday.
The 21-year old, who has been a regular member of the U's first team this year, was stretchered off midway through the first half in his side's 1-0 defeat at the Valley in the build up to Nicky Forster's winning goal.
U's boss Aidy Boothroyd could not give any estimations on the length of time O'Toole would be absent for, but the former Watford player, who signed permanently at the Weston Homes Community stadium in January, is almost certain not to play any further part in his team's push for a play-off place.
"We've lost John-Joe O'Toole to a serious knee injury," Boothroyd told The Green 'Un.
"He has put all his weight on his left knee and has said he felt something crack.
"That's not what you want to be hearing."