The Andalusians were one of Los Blancos’ few bogey teams ahead of kick-off, having avoided defeat in three of the preceding five meetings.
And they nearly shocked their illustrious visitors once again, when Alfonso Espino sent an effort crashing off the post with less than 15 minutes gone.
Real were quick to compose themselves though, and soon created openings of their own, with Marco Asensio and Karim Benzema forcing stand-in goalkeeper David Gil into action before the midway point of an entertaining first period.
Carlo Ancelotti’s six changes to the Real side that beat Chelsea in midweek meant that they struggled to emulate their usual high standards.
Even so, Cadiz still needed a little bit of fortune to make it to the break unscathed, with Benzema smashing the crossbar from 10 yards.
Gil then made a handful of superb stops to deny the visitors, including a brilliant save to deny Dani Ceballos a sensational opener from his wicked volley.
Despite their title defence long lying in tatters, Carlo Ancelotti’s side brought added impetus to their second-half display. Gil was the hero again just minutes after the restart, arching his body to ensure he got a leg to Rodrygo’s one-on-one dinked effort.
That early warning set the narrative for a dominant second-half display from the visitors, with Cadiz restricted to doing damage on the counter attack.
The degree of Real’s dominance only increased as the minutes elapsed, and there was ultimately little the hosts could do about the late double that finally saw them off.
Firstly, Nacho arrowed a 20-yard effort into the bottom corner, before Asensio slid a fine effort into the bottom corner from inside the box.
Winded by the late double blow, Sergio’s men were unable to mount a response in front of their superior visitors, giving Real a vital win in their quest to finish as ‘best of the rest’ behind Barcelona.
As for Cadiz, they would merely settle for 17th place tonight, and must now focus on next weekend’s crunch contest with Espanyol, which could prove crucial in maintaining their top-flight status.