Ronaldo will be out of action for a month after injuring his ankle in Real Madrid’s 3-0 victory over Atletico Madrid at the weekend.
Real said that the Brazilian had suffered a partial ligament tear in his left ankle and would miss up to six matches.
The club were hopeful that Ronaldo would be back for the eagerly-awaited clash with Barcelona on November 20.
The Brazilian left the pitch on a stretcher in the closing minutes after pressurising on Atletico defender Luis Perea to turn the ball into his own net.
Meanwhile, right-back Michel Salgado is out for 10 days after straining a thigh muscle against Atletico.