Los Blancos deserved their triumph, but the hosts challenged them.
Real Madrid scored two late goals to defeat Cadiz in LaLiga Santander on Saturday night.
Los Blancos had been pressing all game, but Cadiz goalkeeper David Gil was inspired. They tried everything but couldn't beat him.
Despite the trip to Cadiz being between two Champions League games versus Chelsea, Carlo Ancelotti named a good lineup, although he made midfield alterations that left older players out.
Muscle exhaustion prevented Vinicius Junior's journey. Eden Hazard played the final 10 minutes.
Real Madrid missed several first-half chances. They were partly to blame for their inaccuracy, but David Gil saved every shot on goal.
Even after Gil was defeated, a disciplined Cadiz backline kept Los Blancos from finishing their opportunities.
Atletico Madrid cannot overtake Real Madrid this weekend, as the distance between Los Blancos and Barcelona is momentarily trimmed to 10 points.