Real Madrid were beaten 2-0 at home to Real Sociedad on Sunday as their season went from bad to worse.
Lucas Vazquez was also sent off for the hosts, who are currently without Gareth Bale and Marco Asensio through injury, meaning he will be suspended for next week's tricky trip to Real Betis.
La Real took the lead after just three minuted at the Bernabeu when Casmeiro fouled Mikel Merino in the box. Willian Jose converted the penalty.
Madrid had the ball in the first half but there shots were largely from distance.
The game opened up after the break -- especially once Lucas was dismissed for a second booking -- and both teams spurned chances.
Vinicius Jr. was Madrid's liveliest player and he caused the most problems, as well as having a penalty appeal turned down.
But the Basque side wrapped up the three points -- their first league win at the Bernabeu since 2004 -- when Ruben Pardo headed in Jose's cross late on.
The loss for Madrid comes just three days after they were held 2-2 by Villarreal. Coach Santiago Solari said that draws should not be underestimated amid criticism of that result. Perhaps his point was proven on Sunday.
Madrid slump to fifth in the table, below Alaves, and could be 10 points behind leaders Barcelona by the end of the weekend if the Catalans beat Getafe later on Sunday.
It doesn't get any easier, either, for Los Blancos. Next up it's Betis away; then it's Sevilla at home.