The announcement by the German Football Association (DFB) that Ballack was struggling with a calf injury is threatening to throw Low's plans for the match into disarray, with the Chelsea man a crucial part of the German side.

However, Low is still hopeful his skipper will be able to face the Spanish, revealing the German medical staff are "working round the clock" to aid Ballack's recovery.

"Michael Ballack, as has already been officially announced, has not been able to train for the past two days," said Low.

"On Friday he had problems with his right calf, the muscle has hardened, and he couldn't possibly participate in the training on Saturday, so we will have to wait and see how things develop overnight."

Low admits he is already making contingency plans in case Ballack does not recover in time.

"Our medical people are working round the clock, but we have to think seriously about what's going to happen if Michael Ballack cannot play," Low added.

"There are two possibilities, Tim Borowski or Bastian Schweinsteiger, both of them can take his position, but we will decide that on Sunday."