The Portuguese winger picked up an ankle injury in Real’s 3-0 victory over Marseille in the Champions League on Wednesday.
Ronaldo suffered the injury while earning his side a 60th minute penalty, which Kaka converted.
Ronaldo went on to play, despite the injury, and scored Real’s third goal.
Gonzalo Higuain came in and replaced Ronaldo with twenty minutes remaining of the game.
Spanish newspaper AS claims Ronaldo’s medical examination has shown that his ankle has suffered bruising and a probable sprain.