Real Madrid suffered a major setback to their La Liga title hopes when they slumped to a 1-0 defeat at Real Betis, handing Barcelona the opportunity to open an 11-point gap over their bitter rivals on Sunday.
Jose Mourinho's side remain eight points behind leaders Barça and five off city rivals Atletico, who they host in the Madrid derby next Saturday.
Betis midfielder Benat Etxebarria's third goal of the season decided the game on Saturday. All of his goals have been hit from outside the area, and he proved once again why Vicente del Bosque has been including him in recent Spain squads.
For Betis, the result comes off the back of a disappointing 5-1 defeat to their local rivals Sevilla last Sunday and puts them four points behind Real in fifth.
Cristiano Ronaldo fired in two shots in the opening exchanges. However, neither side had taken charge of the game when Benat hit what was to be the winner on 17 minutes.
Betis had played the ball into the corner only for Angel Di Maria to badly hook a clearance that the little midfielder controlled before evading the challenge of Sami Khedira to fire a drive past Iker Casillas.
Real continued to enjoy more of the possession and Di Maria twice went close to making amends for his mistake. When Ronaldo crossed from the left, the Argentinian was inches from levelling the game and moments later a Chechu Dorado block looped his goalbound shot over the bar.
Changes no help for Real
Mourinho made two changes at half-time, as he has done on a number of occasions this season. Luka Modric and Kaka replaced Khedira and Mesut Ozil as the Portuguese coach searched for more urgency going forward.
They started brightly, with more purpose, and Ronaldo and Kaka forced good saves from Adrian in the Betis goal. At the other end, Juan Carlos hit a venomous free-kick just over the bar.
Then Mourinho made an early last throw of the dice, replacing Di Maria with Jose Callejon on 62 minutes. Real pressed in search of an equaliser, leaving spaces that Betis were clever enough to expose and Salva Sevilla and Ruben Castro went close for the home side.
Adrian stood firm again to tip over a whipped free-kick from Ronaldo as Real's challenge uncharacteristically fizzled out on a night to forget for Mourinho's side.