Ballack had an operation on his left ankle after being injured in Chelsea's 0-0 draw with Newcastle on April 22 and missed key games including the Champions League semifinal with Liverpool, plus the May 19 FA Cup Final.

British tabloid The Daily Express reported Chelsea are furious after Ballack was operated on against their wishes, although the London club gave permission for the midfielder to fly to Munich to seek a second opinion on the injury.

The article claims Chelsea now question Ballack's commitment as the former Bayern Munich star is unlikely to play for them again this season, but should figure in this June's Euro 2008 qualifiers against San Marino and Slovakia.

But the German Football Federation (DFB) and Ballack have hit back at claims they short-changed Chelsea after he was operated on by German team doctor Dr. Hans-Wilhelm Mueller-Wohlfahrt.

DFB spokesman Harald Stenger said: "Our team doctor informed us, that based on his diagnosis from Friday, an immediate operation was necessary and unavoidable.

"Wohlfahrt detected loose bone splints in Ballack's left high ankle as a result of the injury sustained in the game against Newcastle.

"Any further training session or game could have potentially endangered the player's health, or even threatened Michael Ballack's career.

"Mueller-Wohlfahrt has ensured us that he had informed Chelsea's two physicians before he performed the surgery."

Ballack himself laughed off suggestions he had put Germany's qualification matches over Chelsea's crucial end-of-season games.

"Anybody saying that this operation was done because I was looking at the two Germany games in the beginning of June has to be kidding," he said.

"That's complete stupidity. Name me one player on earth who would risk not playing in the FA Cup final against Manchester United or not playing in a Champions League semifinal against Liverpool because of a Euro 2008 qualifier against San Marino."

The Germans claim that after the Newcastle game Chelsea team doctors treated Ballack's injury, but did not detect cartilage or bone damage.

As the injury did not improve, the 30-year old midfielder took a flight to Munich to consult Mueller-Wohlfahrt, who has treated him for over a decade.

After the operation, one of Chelsea's doctors flew to Munich to assess Ballack's injury, while the midfielder himself is hopeful of wearing the blue shirt again this season.

"I guarantee I did not have surgery for fun," Ballack added.

"I'd much rather be with my teammates to battle Liverpool. But I'm still hopeful I can return in time to play in the Champions League final or in the Premiership this season."

Ballack will stay in Munich for a few days to recover and is wearing a cast on his leg. He will return to London later this week to continue his rehabilitation program.