Kroos entered the squad for Real Madrid against Valladolid on Wednesday, but was knocked out hours later due to an injury.
Real Madrid said in a statement: “The examinations conducted for our player Eden Hazard, by Real Madrid’s medical services, showed that he suffers from a muscle injury in his right leg.”
The statement added, “We are currently waiting for the development of his condition,” in order to know the length of his absence.
Some Spanish reports indicated that Hazard could be absent for up to 4 weeks.
Hazard did not appear in any matches in the new season due to injuries.
Real Madrid will play Valladolid in the fourth round of the Spanish League.