BERLIN - Mario Goetze had the nation at his feet when Germany's hero netted the winner in the 2014 World Cup final.

Fast-forward nearly three years and Monday's news that the Borussia Dortmund star is sidelined indefinitely with a metabolism disorder is the latest blow for the 24-year-old since his Brazil heroics.

"I am in the process of getting treatment and I will do everything I can to get back into training as quickly as possible," Goetze told the club website on Monday.

But there has been an air of frustration around the attacking midfielder for weeks.

Goetze has scored just two goals in 16 Dortmund appearances after returning to his hometown club last summer - a poor return on the $23 million it cost to buy him back from Bayern Munich, which spent $39 million on him in 2013.

Goetze failed to hold down a first-team place at Bayern in three seasons under Pep Guardiola, who preferred the silky skills of Thiago Alcantara to Gotze's industry.

A phone call with Guardiola's replacement, Carlo Ancelotti, towards the end of last term convinced Gotze his future lay in Dortmund - but his return has not been a happy one.

Goetze has played only 11 Bundesliga matches this season, played the full 90 minutes just four times and spent six games on the bench.

A leg injury curtailed him in February and coach Thomas Tuchel dropped him for the home Bundesliga win over second-place RB Leipzig at the start of the month because of poor form.

There has also been external criticism, most notably from Lothar Matthaus, who captained Germany to its 1990 World Cup triumph.

"Quite honestly, even if it sounds a little nasty, if he does not sort it out at Dortmund, he has to go to China, because he certainly won't want to make less money," Matthaus told Sport Bild magazine last week.

"He can't go to (Dortmund's arch rival) Schalke, he wouldn't fit at Bayer Leverkusen, and Borussia Monchengladbach can't afford him.

"Top clubs from abroad no longer have him on their list. He has to change, that is clear.

"He doesn't have the speed, which is everything in soccer today.

"Players like (Bayern playmaker) Xabi Alonso can perhaps compensate for that, but not an attacking player like Gotze."

Dortmund, which is third in the Bundesliga, has given no date for his return and is protective of Goetze, who came up through the junior ranks.

"I am quite certain some people still have to apologize to Goetze - even if they are a big names," said Dortmund's chief-executive Hans-Joachim Watzke in response to Matthaus' comments.

But Goetze is a long way from his dazzling title-winning form for Dortmund in 2011 and 2012.

In a midfield boasting talent like Marco Reus, teenager Ousmane Dembele and Raphael Guerreiro, Goetze faces an uphill battle to once again hold down a first-team place.