Sergio Ramos believes Real Madrid could struggle without Pepe, who is expected to be sidelined for at least a month.
The powerful defender underwent ankle surgery earlier this week and could be out of action for up to four weeks.
"Of course, Pepe's injury will affect the team. He is a great player and has always been very consistent," Ramos was quoted as saying on the club's official website.
"He is a key part of the side and always maintains a very good level of play. Hopefully he will be back soon because he is a very important player in the dressing room and on the field."
Madrid resume La Liga action against Real Sociedad on January 6 after a mid-season break. They sit third on the league table with 33 points from 17 games.