Chelsea's German midfielder Michael Ballack could be considered for the club's USA tour despite preparing to undergo further surgery on his ankle.

Ballack injured his ankle and underwent an operation in May but complications with the healing of the wound have forced him back into hospital.

A spokesman for Chelsea confirmed on Monday: "Michael Ballack will have an operation in Germany tomorrow on his ankle.

"The operation is related only to a complication in the healing of the wound from previous surgery in May."

But Chelsea will wait for a full medical assessment after the operation before deciding whether or not to include Ballack in their tour of the USA which starts in eight days' time.