Real Madrid defender Eder Militao was injured in the 2-0 win over Athletic in the Spanish league matchday 1.
The Brazilian left the field early due to a knee problem. The 25-year-old was later diagnosed with a torn anterior cruciate ligament in his left knee, the club's official website reports.
The recovery time after a cruciate ligament rupture is six to nine months. The same injury was previously diagnosed in the goalkeeper Thibaut Courtois.