English side Chelsea have revealed midfielder Michael Essien's World Cup ended as a result of a complicated surgery.
A statement on the Chelsea website read: "Complications arising from the surgery have meant Michael's recovery has been slower than expected."
A knee injury picked up at the Africa Cup of Nations in January was only expected to be out for six weeks.
But his knee continued to swell up and he underwent surgery four times inside a fortnight.
Essien's last game in a Chelsea shirt was in December last year during a Uefa Champions League game.