Manchester United manager Ole Gunnar Solskjaer fears Paul Pogba could be facing up to three months on the sidelines.
Pogba has not played since the 2-2 draw with Atalanta at the beginning of November, having been banned from Premier League games for his red card against Liverpool.
The midfielder joined up with his France team-mates during the latest international break only to pick up the injury during training.
The initial prognosis was an estimated six weeks out, but Solskjaer on Friday admitted Pogba could be missing for twice that length.
"Sometimes you hope, fingers crossed, for six or seven weeks and the worst-case scenario is 10, 11, 12 weeks with muscle injuries like this," said Solskjaer.
"I'm not a doctor, but he can't say how quickly it will heal. Hopefully just after Christmas we can see him."
Pogba has flown out to Dubai to continue his rehabilitation amid fears he will not play again until 2022.
If the injury is the "worst-case scenario", then United would be without Pogba for 11 games including a trip to Chelsea, the visit of Arsenal and the conclusion of a tricky Champions League group.
