Real Madrid needed two second-half penalties converted by Marco Asensio and Lucas Vazquez to open their Copa del Rey campaign with a 2-0 last 32, first leg win at third-tier Fuenlabrada on Thursday.
Madrid boss Zinedine Zidane gave most of his star names the night off with Cristiano Ronaldo, Luka Modric, Toni Kroos, Isco and Sergio Ramos among those not even included in the squad.
However, Real's reserves failed to take their chance to impress in a sluggish first 45 minutes in which only Marcos Llorente's thunderous volley from outside the box tested Jordi Codina.
"I'm happy, we scored two goals and kept a clean sheet," insisted Zidane.
"We had patience. We knew we could find the gap in the second-half and we did."
Shorn of inspiration from open play, the visitors opened the scoring from the penalty spot when Fran Garcia pulled down Achraf Hakimi just after the hour mark and Asensio slotted home.
Codina temporarily kept Fuenlabrada in the tie with two stunning saves to deny Borja Mayoral.
But Real's second arrived 12 minutes from time when another pull from Paco Candela on Theo Hernandez saw him sent-off for a second yellow card and another penalty awarded to the European champions.