Borussia Dortmund admitted on Wednesday the season is over for Germany's fallen star Mario Goetze as the World Cup winner battles against an a unspecified metabolism disorder.

The World appeared to be at the gifted Goetze's feet in 2014 when he made the difference with a World Cup winning strike as Germany became World Champions.

But his career has gradually gone off the boil since then, culminating in the recent revelation he has metabolism disorder.

"Provided his treatment goes positively, Goetze can start again with performance-orientated training in early summer," Dortmund said.

"The overall sporting goal for the player is to be fully operational for the start of next season," which starts on Friday August 18 in Germany.

The Dortmund website said: "good news for Mario Goetze: Borussia Dortmund's Germany international speaks positively about the first phase of his treatment," but includes no direct quotes.

Last month, Dortmund revealed that medical tests to see why Goetze had been suffering from repeated injury and a lack of form had shown up 'metabolic disturbances'.

Goetze was then sent for specilaist help and Borussia's CEO Hans-Joachim Watzke has said it would not be a "short-term issue".

The now 24-year-old became a national hero scoring in extra-time of the 2014 World Cup final to seal a 1-0 win over Argentina and Franz Beckenbauer once described him as 'Germany's (Lionel) Messi'.

Last July, Dortmund paid 22 million euros ($23m) to buy Goetze back from Bayern Munich, having been forced to sell him in 2013 for 37 million euros after the Bavarians triggered a release clause.

However, poor form and injury meant he has played just six games over the 90 minutes this season and he has been a shadow of the player which left Dortmund in 2013.