Chelsea forward Armando Broja (21) picked up a knee injury in the London club's 1-0 friendly defeat by Aston Villa at the weekend, adding to manager Graham Potter's problems in attack ahead of the Premier League restart.
Broja, who has made 12 Premier League appearances this season, including two starts, was forced off early in Sunday's game in Abu Dhabi after he collided with Villa defender Ezri Konsa.
Chelsea did not provide details on the nature of the injury but British media reported it was serious.
"It doesn't look positive at the moment but it's too early to say. Fingers crossed but it is an awkward one," Potter told the club website.
Chelsea, eighth on 21 points after 14 games, will host Bournemouth on December 27th when the league returns after the World Cup in Qatar.
