Teenage Germany forward Lennart Karl has been ruled out of the World Cup after sustaining an injury in training, the German Football Federation (DFB) said on Friday.
"Lenny tore a muscle bundle today in the final training season and is ruled out because of this injury. Have a good recovery, we're thinking of you," the DFB said on Instagram.
Germany have called up RB Leipzig midfielder Assan Ouedraogo to replace the 18-year-old Bayern Munich player.
Head coach Julian Nagelsmann had said earlier in Chicago ahead of Saturday's friendly against the United States that Karl's injury "didn't look good" and that he had been taken to hospital for a scan.
The loss of Karl is a blow to Germany. He was one of the revelations of the Bundesliga season after making his top-flight debut this season, quickly establishing himself as part of Vincent Kompany's league-winning side.
He started his first match for Germany in Sunday's 4-0 win over Finland, setting up a goal.
Nagelsmann also confirmed that veteran goalkeeper Manuel Neuer would not be fit in time to face the US, but hoped he would return for Germany's first World Cup match against Curacao on 14 June.
Neuer, 40, a World Cup winner in 2014, was surprisingly recalled for the tournament in May, almost two years after announcing his international retirement.
"At his age, he doesn't need a warm-up phase," Nagelsmann said. "He knows how to handle high-pressure situations.
"He's on his way to peak fitness. However, we don't want to take any risks tomorrow."