Neymar was sent off for the first time in his Barcelona career as his side lost ground in the title race in La Liga with a 2-0 defeat at Malaga on Saturday.
Barcelona had a chance to gain on Real Madrid, who were held to a draw earlier in the day by Atletico Madrid, but instead fell three points back of the leaders, who still have a game in hand.
Sandro gave Malaga the lead in the 32nd minute when he chased down a long ball from Juan Carlos and slotted past Barca keeper Marc-Andre ter Stegen.
Neymar had earlier been booked for time-wasting, and he became the first Barcelona player to be sent off in La Liga since October 2015 after fouling Diego Llorente in the 66th minute.
Barcelona thought they had a penalty with eight minutes to play, but the referee controversially ruled that Sergi Roberto was outside the box, and substitute Jony sealed Malaga's win with a stoppage-time goal on a counter-attack.
Real Madrid's La Liga title hopes were dented after they were held to a 1-1 derby draw by Atletico Madrid at the Santiago Bernabeu.
Pepe's second-half header had looked like ensuring Zinedine Zidane's side would remain top of the table, whatever the result when Barcelona face Malaga later on Saturday, but Antoine Griezmann's equaliser meant the European champions' lead only extended to three points ahead of Barca's match.
Atletico remain 10 points behind their local rivals and kept their hold on the third and final automatic Champions League spot, with the point meaning Sevilla will be unable to draw level with them this weekend.
Cristiano Ronaldo's shot headed off the line was the pick of the first-half chances, and Madrid finally made the breakthrough on 52 minutes when Toni Kroos' free kick was headed in by Pepe for the defender's first goal since September.
However, with just five minutes remaining, Griezmann slotted home for his third goal in his last four appearances at the Bernabeu to claim a vital point for Atletico and hamper their rivals' title hopes.
Sevilla were celebrating victory for the first time in over a month after beating Deportivo La Coruna 4-2 -- although the hosts had it far from easy at the Ramon Sanchez Pizjuan.
Jorge Sampaoli's men were without a win in six matches, during which time they had slumped down to fourth in La Liga and knocked out of the Champions League, but they were given a flying start as Stevan Jovetic put them ahead inside the opening minute.
Gael Kakuta levelled moments later but Sevilla were back in front by the ninth minute thanks to Pablo Sarabia. The frenetic opening continued with both teams scoring again before the 32nd minute, with Kakuta equalising for a second time only for Joaquin Correa to put Sevilla 3-2 up.
That is the way the score remained until two minutes from time, when Sevilla, who had honoured departing sporting director Monchi'' before the match, finally finished off Depor with top scorer Wissam Ben Yedder netting his 10th league goal of the season.
In Saturday's early kick-off, Espanyol kept themselves in the hunt for a Europa League spot at the expense of Alaves with a 1-0 win at the Estadio Cornella-El Prat.
Pablo Piatti's goal 11 minutes into the second half was enough to give the Barcelona-based side a fourth-straight home win and move them on to 46 points, four behind sixth-placed Athletic Bilbao having played the same number of matches.
However, Real Sociedad and Eibar both have a game in hand on those two clubs. Alaves remain 11th in the table on 40 points after suffering a third consecutive league defeat.