Dani Carvajal has been laid low by a pericardium virus, with no set date for the defender's return, and Zidane has asked for a new fullback to be signed.
Diario Sport says Perez has agreed and feelers are already being sent out to potential targets. Real Sociedad fullback Alvaro Odriozola features high on the agenda.
Carvajal, meanwhile, is angered by the developments. The defender feels Zidane has been too quick to write him off and believes he deserves better support and patience as he overcomes his setback.
Having seen off Danilo, now of Manchester City, over the past year, Carvajal fears he now faces a new battle to re-establish himself. The defender particularly question the haste Real are showing in seeking a replacement for him with other positions - notably striker - remaining untouched despite the lack of squad options.