Arsenal's Mesut Ozil has been sidelined for up to 12 weeks with a knee injury.
The 25-year-old midfielder, who is on international duty with Germany, played the full 90 minutes in Arsenal's 2-0 defeat against Chelsea at Stamford Bridge on Sunday.
However, according to reports in Germany, Ozil's injury was sustained before he arrived at the World Cup winners training camp on Wednesday.
Ozil faces the possibility of missing 15 games, including high-profile encounters against Manchester United, Borussia Dortmund and Liverpool.
Arsenal are currently facing an injury crisis in central midfield following injuries to Mikel Arteta, Aaron Ramsey and now Mesut Ozil.
Ozil has been heavily-criticised concerning recent performances, but helped the Gunners' win the FA Cup last season - the club's first trophy in nine years.
A statement on the German Football Association website read: "The MRI examination revealed a partial rupture of the outer band of the left knee joint.
"The treatment is six weeks of immobilisation of the knee joint. Mesut Ozil is likely to be [out for] 10 to 12 weeks."
Ozil complained of a sore knee after the defeat at Chelsea on Sunday and Arsenal say they advised the German FA of the situation. The former Real Madrid player has now returned to the Gunners for further assessment.
"It is too early to say how long Ozil may be out of action," said Arsenal in a statement on the club website.