Real Madrid were sensationally held to a 0-0 draw by Olimpic Xativa at La Murta on Saturday.
Free-scoring winger Gareth Bale missed the Copa del Rey first-leg clash due to a bout of flu, while Cristiano Ronaldo sat out the game through suspension, so coach Carlo Ancelotti opted for an attack consisting of Alvaro Morata and Jese Rodriguez alongside Angel Di Maria.
Casemiro could have opened the scoring early on but he headed a Di Maria cross straight at Xativa custodian Francis, who collected comfortably.
The Brazilian midfielder's attempt was Madrid's only shot on target despite a dominant first period, as Los Blancos were comfortably contained by their spirited hosts.
Marcelo was introduced after the break to inject more impetus, but Isco missed a golden opportunity to fire his team into the lead when he sliced Di Maria's pass wide.
Isco was then thwarted by Francis on the hour-mark as the 30-year-old flew full-stretch to deny the former Malaga attacker.
Madrid's defence had been relatively untroubled by their opponents up until that point, but Xativa reminded Iker Casillas they were still in the match when Pepin next fired a rasping shot just over the bar.
Jese then saw his strike creep agonisingly past the post as Madrid sensed a breakthrough, but they just could not find a winner, with substitute Karim Benzema missing a gilt-edge chance to nick it for the visitors when as he toe-poked past the post late on.
Ancelotti's side may now have to call upon the likes of Bale and Ronaldo for the second leg at the Santiago Bernabeu on December 18 to seal their place in the next round.