The club did not give an exact timeframe for Hernández's return, but sporting director Hasan Salihamidzic spoke of "several weeks" immediately after the game in Greece. Hernández' absence will deepen Bayern's defensive worries as the injury comes just days after Germany defender Niklas Süle was ruled out with a ruptured anterior cruciate ligament in his left knee. Süle could miss the rest of the season.
Bayern midfielder Javi Martínez was forced off at halftime in Greece while Serge Gnabry took a knock to his knee, but the club said neither was seriously hurt and "both will do reduced training over the coming days."
Hernández had only recently returned after taking a knock to his right knee in Bayern's win at Paderborn on Sept. 28, and the club was annoyed with the French soccer federation for calling him up and then playing him for the full game in a European Championship qualifier against Turkey.
However, after returning, the 23-year-old played the full game for Bayern against Augsburg on Saturday, and started the game against Piraeus. Hernández was recovering from injury when he joined Bayern for a club-record 80 million euros ($90 million) from Atlético Madrid in July. He was out for months after an operation on March 29 to repair the medial collateral ligament in his right knee.
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