The former Porto centre-back is expected to be unavailable for at least four weeks due to injury, and his team-mate is concerned that his absence could hurt Los Blancos
The powerful defender underwent ankle surgery earlier this week and could be out of action for up to four weeks due to the knock.
"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 brief winter break. They currently sit third in the league table with 33 points from 17 games.