كتب : Sherif Tarek
The Italy skipper couldn't finish his side's training session on Friday after picking up the injury, Real said on their official website.
On the bright side, defensive duo Christoph Metzelder and Pepe has reached full recovery.
Portuguese central defender Pepe is expected to deputize for the veteran Cannavaro in the Primera Liga game against Recreativo.
The 35-year-old had torn ankle ligaments last June and subsequently missed EURO 2008.
He made his comeback several months later, and now he has been sidelined again.
The defending champions are facing a turbulent spell, following unsatisfying results on all fronts.