A late goal from substitute Juan Albin gave Espanyol a 2-2 draw against stuttering Real Madrid who will be 13 points off La Liga leaders Barcelona if they beat second-placed Atletico Madrid later Sunday.
The pressure is now firmly on coach Jose Mourinho with the reigning champions unable to beat relegation-threatened Espanyol.
Cristiano Ronaldo equalised for Madrid on the stroke of half-time after Sergio Garcia had put joint-bottom Espanyol ahead on the half hour mark.
Two minutes after the restart, Fabio Coentrao put Real ahead but it was not enough as Albin slotted home from close range two minutes from the end.
Mourinho had already criticised his players for a lacklustre performance in a midweek Spanish Cup game where they lost to Celta Vigo.
He will be even more frustrated after his side failed to wrap up Sunday's game.
Barcelona have won 14 of their first 15 games in a record start in La Liga and a win against Atletico would be a significant blow in the title race.
Jose Callejon was given the job of leading the Real line with Gonzalo Higuain and Karim Benzema both injured.
Angel Di Maria, who is widely believed to be one of the players that Mourinho was referring to for not giving their all against Celta, started on the bench.
Madrid pressed forward from the start with Ronaldo firing past the post from 25 yards and then moments later poking a pass to Luka Modric who should have at least hit the target with a shot inside the area.
New Espanyol coach Javier Aguirre has worked hard on making the defence more solid but he was without captain and first choice keeper Cristian Alvarez and so put his faith in the inexperienced Francisco Casilla to cope with the intimidating Bernabeu.
Casilla first parried a Ronaldo shot and then Pepe wasted an excellent opening when he headed a Mesut Ozil cross straight at him.
There were warning signs at the other end when Simao struck a weak effort when well placed on the left of the area and then Garcia failed to connect with a long ball from playmaker Joan Verdu which would have put him clear on goal.
Modric hit the post for Madrid with a long distance drive midway through the first half while Wakaso Mubarak was pulled off by the Espanyol coach after some wild challenges having already been booked.
Garcia put the visitors ahead with a clinical finish from a Verdu pass that split the Madrid defence and silenced the crowd.
Ronaldo was denied again by Casilla before he did finally put the ball in the back of the net as he knocked in a cross from Sami Khedira.
After the break Madrid had more of a cutting edge and Coentrao, bursting forward from full-back, latched onto a Ronaldo pass and slotted the ball past Casilla.
The Espanyol shot-stopper was in inspired form though as he prevented Madrid from killing off the game by denying Callejon and substitute Di Maria before also tipping a powerful strike from the latter onto the crossbar.
Madrid were made to rue their missed chances as Albin knocked the ball in after a goalmouth melee as the home side desperately sought to clear the ball.
Earlier, Valencia suffered their first defeat under coach Ernesto Valverde as they fell 1-0 at home to Rayo Vallecano.
Chori Dominguez scored from the penalty spot after Tino Costa upended Roberto Trashorras.
A first-half strike from Ruben Garcia gave Levante a 1-0 win away to Zaragoza.