Real Madrid crashed to a 4-0 defeat at third-division side Alcorcon in a Copa del Rey round of 32 match yesterday.
The result reflected the run of play, with the tiny team from a Madrid suburb outplaying the European giant.
Earlier, Atletico Madrid ended its recent run of dire results by beating third-division Marbella 2-0. La Liga contender Sevilla beat third-division Atletico Ciudad 4-2 with two goals from Luis Fabiano; and Recreativo Huelva drew 1-1 with Sporting Gijon.
On Wednesday defending champion Barcelona will play Cultural Leonesa.
The return legs will be played on Nov. 10.
With a string of poor results recently, including a home defeat to AC Milan and a goalless draw against Sporting Gijon last week, Madrid coach Manuel Pellegrini was already under pressure before this game.
Real Madrid director general Jorge Valdano apologized to fans afterward.
"We have to learn a lesson about humility (with this result)," he said. "I'm convinced that our group of very good players and professionals will turn this result around." When asked whether the Chilean coach's future at the club was in doubt, Valdano replied: "It's not the moment to answer that question."
Pellegrini rested Kaka and played Jose Maria "Guti" Gutierrez as a creative midfielder in Alcorcon's 3,000-capacity Santo Domingo Stadium.
The home side made its intentions clear after two minutes when a long-range shot by Sergio Mora, who tormented Madrid, was just pushed wide by Jerzy Dudek. Seconds later Ruben Sanz nearly lobbed the goalkeeper. A third attempt, this time by Fernando Bejar, was just wide.
In the 16th Alcorcon's constant pressure paid off when Francisco Borja drifted along the edge of the area with the ball, sending his left-footed shot into the bottom corner.
Three minutes later Karim Benzema grazed the bar for Madrid.
Defensive chaos put the host 2-0 up in the 22nd when Madrid's Alvaro Arbeloa charged toward his own goal to gather the ball and misjudged, toe-punting it into the net.
Real finally started to string some attacks together and Rafael Van der Vaart drew a diving save from Juan Manuel Barrero in the 28th.
Possession was shared evenly during the first half although Alcorcon looked more dangerous with the ball.
Alcorcon's Fernando Bejar nearly scored in the 32nd when he headed a cross against the post.
In the 37th, Raul Gonzalez had his best chance of the night only to blast over from 10 meters (yards).
Three minutes later Alcorcon struck again, the unmarked Ernesto Gomez tapping in from a Mora cross.
Seconds later Bejar was through with only Dudek to beat, but the 'keeper just managed to trap the ball with his legs.
The increasingly frustrated Guti received a yellow card just before halftime for a challenge on Mora and during the break he was replaced by Fernando Gago.
Seven minutes into the second half Borja stroked in his second after Dudek failed to clear a dangerous Alcorcon cross.
It was almost 5-0 seconds later when Diego Cascon just failed to slide onto Mora's pass into the area.
Ruud van Nistelrooy, back from injury, replaced Raul for the last 20 minutes.
With the clock ticking down Madrid cranked up the pressure, but last-ditch defending from Alcorcon kept the visitors off the scoresheet.
In Quique Sanchez Flores' first game as Atletico coach following the sacking of Abel Resino last week, the Madrid team took the lead in the 18th minute through an own goal by Marbella. Maxi Rodriguez scored the second eight minutes from fulltime.
Atletico took control of the midfield during the first half yet had few scoring chances.
In the 18th, Marbella's Antonio Troyano misjudged his attempt to chest the ball back to goalkeeper Alejandro Avila, putting the visitors 1-0 up.