Germany winger Marco Reus will be assessed in hospital after rolling his ankle during the team's 6-1 friendly win over Armenia on Friday night.
Reus, who has enjoyed a wonderful season with Borussia Dortmund, had been tipped to light up this summer's event but now his participation looks in doubt as he was seen crying on the side of the pitch after being taken off.
After the game, coach Joachim Loew said: "We can only hope that he will be OK. But it looked bad. We can call up another player until 24hrs before the first game."
Germany face USA, Portugal and Ghana in Group G, with their first game against Portugal on June 16.