Iberian bid loses Ronaldo to injury
The Portugal forward missed training in the morning and needs treatment over the next 24-48 hours, the club said on their website.
Real's top scorer picked up the knock in his side's 5-0 defeat away to Barcelona in La Liga on Monday, and is a doubt for the visit of Valencia on Saturday.
The Iberian bid team present their case in Zurich on Thursday. They are up against Netherlands/Belgium, England and Russia for the right to stage the 2018 tournament.