Karim Benzema's second-half goal was in vain as Real Madrid were beaten 2-1 by Espanyol
Real Madrid slipped to their "worst defeat of the season", according to coach Carlo Ancelotti, following up a shock Champions League reverse with their first Liga loss of the season, going down 2-1 at Espanyol on Sunday
Real, who lost to Moldovan minnows Sheriff Tiraspol on Tuesday, blew a chance to pull ahead of Atletico Madrid, who beat crisis-hit Barcelona 2-0 on Saturday to draw level with their city rivals on 17 points.
Real Sociedad are also on 17 points after they too missed the chance to go top when they were held to a 1-1 draw at Getafe on Sunday.
"There is not much to say," admitted a crestfallen Ancelotti after a defeat that leaves Real without a win in three games after they were held to a goalless draw by Villarreal in their previous league match.
"We did not manage to keep our calm, to put in place what we had planned. The team was not well set-up, with or without the ball.
"You have to be honest. It's the worst game of our season."
Espanyol took the lead on 17 minutes at the RCDE Stadium in Catalonia when Raul de Tomas found the net.
Aleix Vidal scored a sparkling second goal after nutmegging Nacho and smashing the ball past Real 'keeper Thibaut Courtois 15 minutes into the second half.
Karim Benzema had the ball in the net early in the second half but the goal was ruled out for Luka Jovic's offside.
Just as Espanyol appeared to be about to extend their advantage again, Benzema pulled a goal back on 71 minutes, firing into the bottom corner after the French international collected a pass from Jovic for his ninth league goal in eight games this season.
Espanyol had won just once in seven games this season but they hung on grimly in five minutes of added time to take all three points.
"We now need to use the international break to think about why this team's attitude has changed in the space of a week," said Ancelotti.
"But this defeat is no accident. We didn't play well."
Victory for Sociedad would have shunted them to the top of the table but they had to settle for a point after Mikel Oyarzabal produced a 68th minute equaliser to cancel out Sandra Ramirez's opener for Getafe five minutes before half-time.
The point was Getafe's first of the season after seven straight losses.
A goal in each half from Dutch international Arnaut Danjuma saw Villarreal bounce back from their midweek defeat at the hands of Manchester United in the Champions League with a 2-0 win over Real Betis while a lone strike from Dario Benedetto gave Elche a 1-0 win over Celta Vigo.