United States international Timothy Chandler is to undergo surgery and will be out "for the foreseeable future" after suffering a lateral meniscus tear during Eintracht Frankfurt's 2-2 draw with Borussia Dortmund on Saturday.
Chandler went down without being touched by an opponent 10 minutes before half-time against Dortmund and had to be replaced by Carlos Salcedo.
Frankfurt announced on Monday that tests have shown the 27-year-old will require surgery "after suffering a lateral meniscus tear in his right knee."
A statement on the club's official website added that they "will be without first-choice right-back Timothy Chandler for the foreseeable future."
While the defender had played every minute of Frankfurt's Bundesliga campaign this season, he was not selected by then-United States head coach Bruce Arena as the nation failed to qualify for the 2018 World Cup earlier this month.