Captain Ebu Bekir Is went off injured after 27 minutes of Germany's U19 European Championship qualifier against Portugal.
After just over 23 minutes, the Eintracht Frankfurt youngster threw himself in front of an opposition shot and appeared to twist his knee. Bekir Is tried to play on after brief treatment on the pitch, but the pain was too great.
He collapsed on the pitch again, prompting coach Hanno Balitsch to replace the 18-year-old with Elias Arden. Bekir Is looked dejected as he left the pitch and struggled to hold back tears.
Earlier, Bekir Is had helped set up the German side's opening goal against Portugal, playing a fine pass in behind for Maik Akumu in the 19th minute.
How long will Ebu Bekir Is be out after his injury?
Whether Bekir Is will be sidelined, and for how long, remains unclear. At SGE, he plays primarily for the second team in the Regionalliga Südwest and usually operates in defensive and central midfield.
Germany's U19s ultimately lost an entertaining match against Portugal 2-3 (1-1). Balitsch's side led 2-1 until around ten minutes from the end, but two late goals turned the match in Portugal's favour.
With three points from two matches, Germany's U19s sit second in the table behind Portugal. They won 2-1 against Sweden in their opening European Championship qualifier, with Lithuania their next opponents.