Madrid:FC Barcelona failed to regain the lead in the Spanish league when it conceded a 1-1 draw to Real Betis on Rafael Sobis' 89th-minute goal on Sunday.
Defending champion Barcelona was second to Real Madrid on head-to-head results in the standings.
Ronaldinho scored first from the penalty spot at Camp Nou but Barcelona coach Frank Rijkaard replaced him in the second half for the first time this season, then Sobis took advantage of some slack defending.
Barcelona's disappointing result came three days after its humiliating 4-0 loss at Getafe, which cost the team a place in the Copa del Rey final.
"We're all down, we're all affected," Rijkaard told news agency Efe. "We still have a chance of winning the league. We can't allow our heads to drop."
Also on Sunday, fourth-place Valencia maintained its slim title hopes with a 2-0 win over fifth-place Zaragoza.
Defender Emiliano Moretti and David Silva each scored in the first half to virtually assure the 2002 and 2004 champion of a berth in next season's Champions League.
With four games remaining, Madrid and Barcelona each have 66 points, two more than Sevilla. Valencia has 62, and Zaragoza 55.
Also, Fernando Torres scored his 11th and 12th goals of the season to help Atletico Madrid defeat Getafe 4-1 and boost its hopes of a place in next season's UEFA Cup.
Elsewhere, it was: Gimnastic Tarragona 1, Real Sociedad 3; Celta Vigo 1, Levante 2; Athletic Bilbao 1, Deportivo La Coruna 1; Osasuna 1, Villarreal 4; and Racing Santander 0, Mallorca 2.
Barcelona midfielder Deco, who returned to the team along with forward Lionel Messi, was fouled by defender Juan "Melli" Andreu and Ronaldinho converted his seventh spot kick of the season for his 18th goal overall.
The hosts spurned several chances to increase their lead before halftime, while Betis forward Fernando Fernandez almost scored in the 44th following a mistake by Lilian Thuram.
Betis, which went into the game winless in eight games, then improved, leading Rijkaard to replace Ronaldinho and Messi midway through the second half.
With Barcelona growing increasingly anxious, Betis substitute Isidoro Gomez forced goalkeeper Victor Valdes into a good save in the 86th minute.
Valencia takes lead
Valencia took the lead in the 21st minute when Moretti clipped home Silva's volley for his first goal of the season.
Zaragoza goalkeeper Cesar Sanchez prevented a second goal when he dived to parry David Villa's penalty seven minutes later.
Cesar also denied Villa in the 44th but the ball ran to Silva, who sidefooted Valencia's second goal from a narrow angle.
Torres scored his first goal in the second minute after controlling the ball with his head.
Midfielder Maniche doubled the lead with the outside of his right foot in the 18th minute following another counterattack.
Getafe, which meets Sevilla in the Copa del Rey final on June 23, replied through Manu Del Moral's shot in the 60th. Torres doubled his tally after rounding goalkeeper Roberto Abbondanzieri four minutes later to make it 3-1, and Atletico midfielder Luciano Galletti converted an 88th-minute penalty.
The victory ended a three-game winless run for Atletico, keeping it in sixth place with four games remaining.
Getafe dropped to ninth place.
Sociedad boosted its fight against its first relegation in 40 years and left last-place Gimnastic virtually certain to go down.
The Basque team, which climbed to 18th place, took a two-goal lead through Gaizka Garitano's 12th-minute header and Savio Bortolini's 24th-minute shot.
Javier Portillo reduced the deficit in the 31st, but Ion Ansotegi scored Sociedad's third in the 72nd.
Celta, trying to avoid the drop, lost to fellow struggler Levante and slipped to 19th place.
Gustavo Reggi's penalty in the 39th and Mustapha Riga's shot 10 minutes later gave Celta its fourth straight defeat in five games under coach Hristo Stoitchkov.
Fernando Baiano scored Celta's goal in the 62nd.
Bilbao, fighting to avoid dropping into the second division for the first time, moved four points clear of the relegation zone by drawing with Deportivo.
Bilbao defender Ander Murillo headed home in the 57th, with Ivan "Riki" Sanchez-Rico leveling for the visitors six minutes later.
Deportivo's Joan Capdevila was ejected in the 78th and was followed in injury time by Bilbao's Josu Sarriegi.
Diego Forlan scored in the 64th, 87th and 90th to bring Villarreal its fourth straight win.
Former France midfielder Robert Pires gave the visitors a seventh-minute lead with Osasuna midfielder Valdo Lopes leveling 10 minutes later.
A 10-man Santander extended its winless streak to four games against Mallorca.
The hosts, whose forward Pedro Munitis was sent off in the 21st, fell to goals from Fernando Navarro and Juan Arango early in the second half.
On Saturday, Madrid edged Espanyol 4-3 and Sevilla beat Recreativo 2-1.