Germany captain Michael Ballack has been ruled out of the World Cup curtain raiser against Costa Rica on Friday.

The Chelsea midfielder suffered a calf strain during the 3-0 warm-up victory against Colombia last weekend but his recovery progressed quickly enough for him to resume full training on Wednesday.

However, he was unable to complete the session after experiencing pain in his calf and coach Jurgen Klinsmann has now been forced to change his plans for the Group A clash.

Klinsmann said: "He is not available. Ballack was forced to end practice yesterday after 30 minutes and it does not look as if he will be able to play tomorrow against Costa Rica.

"We want a fully fit Michael Ballack, not a 50 per cent player. Fingers crossed he'll be back training soon."

Ballack's place in the starting line-up is likely to go to either Werder Bremen's Tim Borowski or Borussia Dortmund's Sebastian Kehl.