Chelsea utility man Michael Essien is an early doubt against Manchester United on September 21 after injuring his ankle.
The Stamford Bridge powerhouse hobbled out of Ghana's World Cup qualifier against Libya on Friday and could now be out of action for up to four weeks.
Luiz Felipe Scolari's title-chasers face Manchester City at Eastlands next weekend and Essien is optimistic he will be ready, but accepts the injury could rule him out.
He told Sky Sports: "My injury? It is serious but I can be ready again soon."