Isco did not start Real Madrid's Copa del Rey round of 16 game against Leganes due to the importance of the fixture, according to Santiago Solari.
Real claimed a 3-0 victory in the first leg of the tie thanks to goals from Sergio Ramos, Lucas Vazquez and Vinicius Junior, the former netting his 100th career strike.
Solari had a growing number of injuries ahead of the cup game, including knocks to Gareth Bale and Marco Asensio. But Isco, who has been given limited game-time this term, was not selected to start and settled for a role as a 71st minute substitute.
Despite his lack of opportunities, Isco previously insisted he does not want to leave Santiago Bernebeu in January.
When asked about his team selection after the game, the Madrid boss told reporters: "There's 24 players and my duty is to pick the players. It's not the most pleasant duty.
"Why Isco didn't play today as starter? Today we made a big game."
Despite the importance Solari placed on the fixture, there were many empty seats at the Bernabeu.
Speaking about the poor attendance, Solari added: "There's hundreds of millions of Real fans around the world. There's Real fans in every country of the world. But not everybody can attend the games at the stadium. Real Madrid is the football global brand. There's always people watching. We always feel the fans."
There was a rare start in goal for Keylor Navas, and the keeper will be getting more first-team action in coming weeks after it was confirmed today that Thibaut Courtois has suiffered a hip injury.
The Costa Rica international has regularly featured for Real in the last three seasons, but has made just two La Liga appearances this term due to the arrival of Courtois from Chelsea.
Solari said of Navas: "He is training very well, he is quite fine. Today he made a big game and it's important for Real Madrid. And he will still be important in the future."
The keeper will be in line to start when Los Blancos play Real Betis on Sunday, three days before they travel to Leganes for the second leg next week.