A deflected strike from Deco gave Barcelona a 1-0 derby win at Espanyol on Saturday, taking Frank Rijkaard's in-form side five points clear at the top.
Deportivo Coruna moved up to fourth on 11 points with a 2-1 win at home to Getafe but Real Madrid lost further ground as they needed a second-half goal from Ronaldo to claim a 1-1 draw at Real Betis.
With Samuel Eto'o and Ronaldinho both missing good chances, Deco's ninth-minute blast was all Barca had to show for another vibrant attacking display but disappointing Espanyol only occasionally threatened a comeback.
The result gave unbeaten Barcelona 19 points from seven games and left Valencia, in second spot with 14 points, needing victory at home to third-placed Sevilla on Saturday to stay within striking distance.
Real Madrid are in 10th place with 10 points after another unconvincing league display, salvaged only by Ronaldo's second goal of the season.
Real, with Guti in for the injured David Beckham, showed plenty of fight against Betis but produced precious little good football and were grateful to Iker Casillas for keeping them in the game.
GREAT SAVES
The Spain keeper made two outstanding saves from Ricardo Oliveira after sweeping breaks from midfield before the Brazilian striker finally made the breakthrough at the third attempt.
Fernando showed great control to shield the ball and touch on a pass to Edu, who did equally well to hold off the Real defence and find Oliveira in space to drill a shot past Casillas.
Stand-in Real coach Mariano Garcia Remon, still struggling to make an impact following Jose Antonio Camacho's shock departure, responded by bringing on Michael Owen in place of defender Walter Samuel.
Owen hardly threatened to score his first goal for Real but the presence of the England international gave Betis more to worry about in defence and the visitors began to gain control.
Zinedine Zidane was just wide with a low volley in the 59th minute and six minutes later the French midfielder teed up Ronaldo for the equaliser.
Real had the better of the remaining 25 minutes and twice went close to a winner, Roberto Carlos flashing a free kick a fraction wide and Zidane forcing a good save from Prats with a snap shot in injury time.
"You have to recognise that Betis were the better side in the first half," said Garcia Remon. "After the break we were a lot better, though, and we had the chances to win.
"We're not playing as well as we'd like to but we must have hope."
