Real Madrid defender Ricardo Carvalho has suffered a knee ligament injury, the club have revealed.
The 33-year-old has made just eight appearances for Madrid this season and only recently returned to training after a back problem that had forced him out for over a month.
The club have yet to set a date for his return, but the injury could see the Portugal international miss the Clasico on December 10.
Carvalho last appeared for Los Blancos in September, when the Spanish league leaders beat Ajax 3-0 in the Champions League.
