Schalke's American midfielder Weston McKennie will miss the next six weeks after partially tearing the medial collateral ligament in his right knee on Sunday.
The Bundesliga club announced the results of a scan on Monday, a day after the 19-year-old was injured in a 1-1 draw with Hannover.
McKennie left the game after 20 minutes after coming together with Hannover's Felix Klaus.
The FC Dallas youth product has made 17 appearances for Schalke this season, including nine starts in the Bundesliga.
His club form earned him a first cap for the U.S. national team in November, when he scored in a 1-1 draw in Portugal.
He is now set to miss Schalke's next six Buyndesliga games as well as the DFB Pokal quarterfinal against Wolfsburg.