Barcelona lost 1-0 at home to Rayo Vallecano, meaning Real Madrid could boost their plans for the trophy.
This was the third consecutive home defeat for the Catalans, the second time Barcelona had faced such a fate in their history, and Alvaro Garcia’s early strike was a difference between the two teams.
It means Real Madrid are top of the table with 15 points with five games to go, putting Los Blancos in contention for the title.
That will be confirmed if Carlo Ancelotti’s side avoids defeat by Espanyol next Saturday, and Xavi’s Barcelona reduces their hold on to second place with this comeback.
Vallecano, who sits 14th in LaLiga before their arrival at the Camp Nou, snatched a goal in the seventh minute when Garcia ran into space to meet a sharp pass from Isi Palazon and fired a sharp shot in the lower right corner.
Jordi Alba curled a shot wide of the post as Barcelona chased the equalizer, while Gavi claimed a penalty when he crashed to the ground under an empty challenge from Santiago Comesana. Referee Isidro Diaz de Mera Escuderos was not impressed and booked coach Xavi to pass his complaints on.
A clever floating shot from Gavi hit the crossbar just before half-time, and although Ferran Torres blocked the ball from the net from a double, he was still offside.
Alba was sidelined as Barcelona pushed early in the second half, but the home side were terribly down, Ferran Torres and Frenkie de Jong were replaced by Memphis Depay and Nico Gonzalez as Xavi looked to add strength.
Depay had a short shot blocked by Nikola Maras, and the Dutch striker saw a 20-yard touchdown pass by Stole Dimitrievski, but the equalizer did not arrive.