Raphael Varane is currently under observation by Real Madrid's medical staff after being forced off with a head injury in Saturday's LaLiga win at Eibar.
Replaced by Nacho after clashing with Eibar's Kike
The Frenchman had to be substituted shortly before the half-hour mark at Ipurua after suffering a clash of heads with Eibar striker Kike García minutes earlier.
After receiving treatment in the immediate aftermath of the incident, both Kike and, initially, Varane remained on the field.
However, with the defender complaining of dizziness and showing significant swelling above his right eye, he asked to be brought off and was replaced by Nacho Fernández.
Real are expected to provide further details on the player's condition in the coming hours.
Ronaldo double secures all three points for visitors
Two goals by Cristiano Ronaldo, either side of an equaliser by Iván Ramis, saw Zinedine Zidane's men run out 2-1 winners in the Basque Country.