Alvaro Morata is now a doubt for Chelsea's trip to Brighton and Hove Albion this weekend, after he limped off in their Europa League clash with MOL Vidi.
Morata landed awkwardly on his left leg just before he saw his shot saved by the Vidi goalkeeper.
The Spanish striker immediately fell to the floor, clutching at his knee and was then carried off by the medical team.
Olivier Giroud replaced the 26-year-old; who walked straight down the tunnel due to the injury.
Morata has scored five goals in the Premier League so far this campaign and he was expected to be on the bench against Brighton anyway after starting in Budapest.
This means Giroud is Chelsea's only option as an orthodox striker, but Maurizio Sarri did opt with Eden Hazard in the 'false nine' role in their 2-0 win against Manchester City.