The midfielder's injury appears to be more serious than initially thought and he will most likely miss the Copa del Rey quarter-finals, in which Madrid could face Barcelona
The Germany international sustained the injury in the first half of Madrid's 1-0 victory at Malaga in the Copa del Rey and had to be stretchered off.
Madrid have announced on their website that Khedira has sprained a ligament in his right ankle, and Del Corral, a former head of the club's medical services, has revealed that the former Stuttgart player will take some time to recover.
"If there is an injury to that ligament, it can take several weeks to recover or even a month," he told Cadena Cope.
"The fact that it has affected the anterior syndesmosis makes me be more cautious about his recovery time."
Khedira's four-week injury prognosis will see the 24-year-old miss Madrid's upcoming five league matches in addition to the two-legged Copa del Rey quarter-final, where they are likely to face Barcelona.