Germany head coach Joachim Low has lifted the lid on Chelsea's controversial decision to leave Michael Ballack out of their squad for the Uefa Champions League group stages.

Last Friday was the date for the submission of the list and Chelsea's medical staff could not guarantee Ballack would recover in time, from ankle surgery, to play any part in the Group B matches.

When news of Ballack's omission broke there was speculation linking the German with a Stamford Bridge exit.

Chelsea insist the decision was taken solely on medical grounds but given Ballack is hopeful of making a return at the beginning of November - the group stages conclude on December 11th - talk of a possible departure is almost certain to resurface.

And now, Low has added a further layer of intrigue in his claim that Ballack is at a loss to explain the decision of Chelsea's management.

"I discussed it with Michael and he could not fully explain Chelsea's decision to me," said Low, in a press conference on Wednesday ahead of Saturday's Group D Euro 2008 qualifier against Wales.

"Chelsea's doctors estimate he will not be able to play for two to three more months, but Michael is much more optimistic and expects to play sooner.  For us, Chelsea's decision isn't justifiable."

This is the second time Chelsea and the German camp have failed to see eye-to-eye with regards Ballack.

Chelsea were far from enamoured with Ballack's decision back in April to fly back to his homeland and have ankle surgery, at the behest of German doctors.

The surgery subsequently ruled him out of Chelsea's UEFA Champions League semi-final and the FA Cup final.

The Republic of Ireland face Germany in a Euro 2008 qualifier at Croke Park next month.