Real Madrid have confirmed that Pepe fractured two ribs in the 1-1 draw with Atletico Madrid on Saturday.
The centre-half scored the opening goal in the Spanish capital derby before a collision with teammate Toni Kroos ended his afternoon prematurely.
Antoine Griezmann scored a late equaliser to derail Los Blancos' title hopes, and the day was to get even worse for Zinedine Zidane's side as the extent of Pepe's injury was confirmed.
A Real statement read: "The player has been diagnosed with fractures to his seventh and eighth left ribs. His recovery will continue to be assessed."
Real take on Bayern Munich over two legs in a Champions League quarter-final this month and face a potential title-deciding Clasico against Barcelona on April 23.
