As highlighted by Diario AS, the issue at right-back is causing some level of worry at Madrid ahead of the clash.
However, both Spain internationals are now unavailable for the trip to Anfield with Lucas Vazquez ruled out for the remainder of the campaign through injury.
That means that Alvaro Odriozola is the only recognised right-back remaining in the squad – although Nacho Fernandez can play in that position but will remain central.
Odriozola has started just nine matches for the club over the past two seasons and was loaned out to Bayern Munich last January – but he featured sparingly for the German side too.
Boss Zinedine Zidane is said by the report not to have a great deal of trust in the player and believes that may be exposed at Anfield.