Officials in Turkey believe the intense rivalry between Turkish fans could have prompted the leak after Kewell gave a routine negative sample after the game.

Reports in Turkey today claimed Kewell has autoimmune hepatitis, a non-contagious disease where the body attacks its own liver. The cause of the condition is unknown.

Kewell is understood to have lived with the condition for most of his career without any adverse effect on his abilities.

Treatment for the disease requires a daily dose of the steroid, prednisone.

Medical sources have told au.fourfourtwo.com that Kewell has been given permission by FIFA to use certain drugs to treat his medical condition.

And it is believed details of that approval may have become public at his drugs test after the UEFA Cup game last week, prompting the leak to the Turkish press.

The country boasts seven daily sports newspapers which feed the fierce fanaticism between Fenerbahce and Galatasaray supporters.

It is understood the club believes that rivalry has sparked the leaking of information from the drug test to the newspapers.

Now Harry and his club are in the process of launching legal action against some of the media in Turkey for wildly exaggerating his condition and falsely claiming he was putting team-mates and opponents at risk.

Harry's personal manager, Bernie Mandic, stressed: "Harry does not have and has never had any infectious disease."

Kewell has admitted in the past that his injury woes have worn him down and hinted there was more to his problems than ankle or groin injuries.

“Some of the people who say things know nothing about me or what I’ve been through,” he said.

“If they sat down with me and asked exactly what is wrong, I think they'd change their mind.”