Real Madrid have confirmed that Lucas Vazquez suffered a cruciate ligament injury during the Clasico with Barcelona on Saturday.
Vazquez went down after a heavy challenge with Barcelona midfielder Sergio Busquets and had to be replaced late in the first half as his side went on to beat their rivals 2-1.
It has not yet been determined how long the Spain international will be out of action, but he will miss the rest of the season after the diagnosis was confirmed.
A statement posted on the club’s website read: “Following tests carried out today on Lucas Vazquez by the Real Madrid Medical Services, he has been diagnosed with a sprain to the posterior cruciate ligament in his left knee.
“His recovery will continue to be assessed.”
Vazquez said he is “sad” by the news but pledged to support the capital club from the sidelines as they look to maintain their challenge for La Liga and the Champions League.
The 29-year-old could be on his way out of the Santiago Bernabeu as his contract expires at the end of the season.
The winger also helped his side take the lead inside the first 15 minutes of the weekend’s La Liga encounter.
Vazquez has been a key player for Zinedine Zidane’s side this season, having scored two goals and made five assists in 24 La Liga appearances.