Brazilian duo Marcelo and Vinicius Jnr were all in the starting lineup for Los Blancos but failed to inspire.
Promoted Cadiz set about running the party from the onset and took a deserved lead through Anthony Lozano’s 16th-minute effort.
Thibaut Courtois denied Lozano a second before half-time, when Zinedine Zidane made four substitutions with an injured Sergio Ramos among the players to make way.
Luka Jovic had a goal ruled out and Karim Benzema hit the crossbar, yet Madrid’s sluggish play was not enough to overcome Cadiz’s resolute setup as the Andalusian side held on for a famous triumph.
Prior to his injury, Ramos came to Madrid’s rescue after just two minutes, stopping Alvaro Negredo’s effort off the line.
Negredo went close with a header and Juan Cala tested Courtois with a shot as Cadiz kept up the pressure, though, and the visitors were rewarded for a brilliant start when Lozano prodded in over Madrid’s onrushing goalkeeper.
Lozano looked set to double his tally just after the half-hour, but Courtois made a fine save at his near post, though Madrid’s goalkeeper had a lucky escape when he dropped a cross which no Cadiz attacker could pounce on.
With four new faces on, Madrid improved their game, though Vinicius‘ wayward strike was the closest they came to getting an equalizer in the second half.
Vinicius should have restored parity after the hour; only to head wide from Toni Kroos‘ left-wing cross, the Germany midfielder created five chances as his team-mates struggled.
Jovic’s introduction looked to have sparked the comeback, yet the substitute’s goal was rightly disallowed for an offside from Benzema, who then struck the woodwork as Cadiz held firm to join Madrid and Granada on 10 points.
