Real Madrid have confirmed that defender Pepe has broken two of his ribs.
The Portugal defender scored the opening goal in their 1-1 draw with Atletico Madrid on Satuday with a powerful header.
But he was forced off after a heavy collison with Toni Kroos. Pepe was replaced in the 67th minute with Nacho.
After undergoing medical tests, Madrid later confirmed a double rib break.
“After the examinations carried out today on Pepe at the Sanitas La Moraleja University Hospital, he has been diagnosed with fractures in seventh and eighth ribs on the left side,” a statement from the club read.
This news leaves manager Zinedine Zidane with a major defensive crisis, as the business end of the season sets in.
Raphael Varane is already out with a hamstring problem, leaving Sergio Ramos and Nacho as the only front-line centre-backs.
Madrid travel to Bayern Munich next for the first leg of their Champions League quarter-final clash.