The Germany captain was not among the 23-man list submitted to UEFA last Friday, fuelling speculation he will be sold when the transfer window re-opens.

The decision came to light on Monday, with Chelsea insisting the 31-year-old midfielder out because the club doctors could not guarantee he would be available for the majority of their group games.

They reiterated that position in a statement on Thursday, which read: "Chelsea Football Club would like to reiterate that Michael Ballack's omission from the UEFA Champions League group phase squad list was taken only because of injury.

"There is no other reason for the decision and suggestions to the contrary are unfair on both Michael, who is attempting to get fit as soon as possible, and our medical team in whom we have every confidence."

Ballack has not played since undergoing ankle surgery at the end of April.

He had a second operation at the beginning of July, and Chelsea's claim he will miss the majority of their Champions League group games suggests he will not be ready to return until the end of October at the earliest.

But such a pessimistic prognosis was on Wednesday described as "unjustifiable" by Germany coach Joachim Low, who is eager to have his skipper available for the climax of his side's European Championship qualification campaign.

Speculation has been rife Ballack's omission is a prelude to him being sold, with the midfielder having had an indifferent first season after leaving Bayern Munich for Stamford Bridge.