Chelsea midfielder Carney Chukwuemeka is expected to be out for six weeks after having knee surgery on Monday.
Chukwuemeka, 19, sustained the injury in Chelsea's 3-1 defeat by West Ham in which he scored the Blues' only goal.
A £20m summer signing from Aston Villa, he started in Chelsea's first two Premier League games of the season.
"Minor setback but I'll be back very soon. Thank you Chelsea fans for your love and support."
Confirming Chukwuemeka had undergone surgery, Chelsea added the player would now begin rehabilitation, working with the club's medical department at their Cobham training facility.