Cristiano Ronaldo is a major doubt for Real Madrid's Champions League showdown with Manchester City next week after the club confirmed that he has suffered a thigh muscle strain.

The 31-year-old, who has 47 goals in 46 appearances so far this season, picked up the injury during Los Blancos' 3-0 win over Villarreal on Wednesday evening.

Ronaldo initially looked to have played down fears of any long-term injury post-match at the Bernabeu, but further tests have now revealed that he is facing a potential spell on the sidelines.

Madrid make a short trip to Rayo Vallecano on Saturday afternoon, which will almost certainly come too soon for the Portuguese, while Tuesday's European tie at the Etihad Stadium may also be out of the question.

A club statement read: "Following tests carried out today on Cristiano Ronaldo, he has been diagnosed with a muscle strain in his right thigh. His recovery will continue to be assessed."

Zinedine Zidane admitted on Wednesday that he should have withdrawn his top-scoring attacker earlier against Villarreal to prevent fatigue and injury problems setting in following a gruelling campaign to date.