Thibaut Courtois insists he is still one of the world's best goalkeepers and has accused the Spanish media of wanting to "kill" him.
Although two Eden Hazard goals eventually helped to secure a 3-1 win, Courtois' error has led to further questions over his form this season.
Navas was the incumbent starter for three Champions League runs under Zidane, but was benched in favour of the Belgian when he signed from Chelsea this summer.
However, the 26-year-old Courtois has no doubts over his abilities despite Thursday's error.
"I still consider myself one of the best, despite the Spanish press wanting to kill me," he said, according to El Espanol.
"I feel very strong. I'm calm because I train well and play well.
"It was a small mistake, but that's the life of a goalkeeper. Despite that, afterwards I stayed calm and played my game."
Belgium are set to face another Euro 2020 qualifier on Sunday when the Red Devils, who finished third at last summer's World Cup, take on Cyprus away.
Following that match, Courtois will return to Real Madrid, a club that currently sits third in the league, two points behind second-place Atletico Madrid and 12 points behind league-leaders Barcelona.