Ismael Saibari went off injured against Borussia Dortmund on Saturday evening. Sky Sports Germany report the Bayern München midfielder will be out for months.
A collision with Dortmund goalkeeper Gregor Kobel brought the Morocco international's appearance in Der Klassiker to an early end. Serge Gnabry also went off injured for the home side soon afterwards.
On Sunday morning, Saibari underwent surgery after suffering a syndesmosis injury. That is a tear or strain of the connective tissue between the shinbone and fibula, just above the ankle joint.
Bayern München signed the midfielder and attacker from PSV for €50 million last summer. He will be unable to play for Germany's record champions for at least three months.
Before the injury, Saibari had scored three goals and provided as many assists in fourteen appearances for the club.
Bayern München could not win without Saibari. Former PSV striker Fabio Silva scored late to make it 2-2 after ninety minutes.