Paul Pogba's return to Manchester United's first team has been delayed after the French midfielder fell ill, manager Ole Gunnar Solskjaer has said.
Pogba, 26, has only played six times this season after suffering an ankle injury in September.
Solskjaer is hopeful Pogba will be available before the end of the year, but the latest setback has ruled him out of Wednesday's League Cup quarter-final against League Two side Colchester United at Old Trafford.
"Of all things he's struck down ill now," Solskjaer told reporters.
"He's been off for two or three days – three days probably – so that's not beneficial. That's probably set him back quite a bit.
"We just need to get him match fit. He might be half an hour, 45, 60, 90 minutes – who knows – in the first game. We're working hard to get him back, but now he's ill."
United slipped to sixth place in the Premier League after Sunday's 1-1 draw against Everton. But Solskjaer said he was impressed with academy graduate Mason Greenwood, who scored his seventh goal for United across all competitions this season.
Solskjaer said he is considering giving the teenaged striker a run of games to see if he can extend his purple patch in front of goal over the festive period.
"He's making it hard for me to leave him out," the United manager added.
"I remember when I came to the club and I kept scoring a few goals, and even though I felt I could have performed better, the manager's comments were 'It's hard to keep players who score out of the team'.
"It's very, very difficult now to put a team out there without having Mason in my mind."