Austria international Konrad Laimer suffered an early injury during Bayern Munich's friendly against Leipzig on Saturday. Unable to continue normally, he was forced off the pitch.
Max Eberl, Bayern's board member for sporting affairs, told German newspaper "Bild": "Konny (Laimer) took a knock relatively early, and his foot quickly swelled. So he came off as a precautionary measure."
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Eberl added: "It was clear to the point that he could no longer walk, and he needed someone to help him. You saw that, and he was not moving normally."
How long will the Austrian be out? The Bavarian club's sporting director could offer no timeline. "I really can't say today how long it will take," he said.
The worry over Laimer lands at an awkward time. Bayern are gearing up for the new season, kicking off their official campaign against Borussia Dortmund in the German Super Cup on 22 August.
The Bavarian side beat Leipzig 3-1 in today's match. Luis Diaz, Nathaniel Brown and Jamal Musiala found the net, while Moroccan star Ismael Saibari teed up the third on his first appearance for the record Bundesliga champions.