FC Barcelona closed in on the leaders after their first away victory against Real Madrid CF since 1997.
Barça came from behind with goals from Patrick Kluivert and Xavi Hernández to claim a breathtaking 2-1 triumph but Valencia CF failed to take advantage of Madrid's slip, drawing 1-1 at Athletic Club Bilbao.
Barça's win put the Catalan side firmly in contention for the title with four matches remaining - and provided Ronaldinho with a stage to showcase his talents in the absence of his injured compatriot Ronaldo. Xavi, Roberto Carlos and Ronaldinho all went close in the first half but it was not until the 53rd minute that Santiago Solari opened the scoring with an angled shot from inside the box.
Barça were soon level as Giovanni van Bronckhorst lobbed a cross over Iker Casillas and Kluivert was perfectly placed to bury a header. Ten minutes later, former Azulgrana favourite Luís Figo was sent off for a second yellow card. The visitors capitalised on their numerical advantage and Xavi scored the winner in the 86th minute after exchanging passes with Ronaldinho.
In Valencia's meeting with fifth-placed Bilbao at San Mamés, Jorge López was fortunate to squeeze a penalty under goalkeeper Daniel Aranzubia for the opener in the 14th minute. Asier del Horno equalised for the Basque side on the half-hour, escaping his marker at a free-kick to head in. Both teams had chances to take all three points but neither could apply the decisive finish.
On Saturday, Málaga CF dented RC Deportivo La Coruña's hopes of a third-place finish by holding the Galician outfit to a 1-1 draw at La Rosaleda. Víctor gave the UEFA Champions League semi-finalists the lead but Manuel Canabal levelled for the hosts four minutes before half-time.
At the other end of the table, two late goals from Fernando Correa ensured RCD Mallorca moved out of the bottom three with a 3-1 win at fellow strugglers Real Valladolid. The result lifted the islanders into 14th place and meant that RCD Espanyol dropped back into the relegation zone despite a 3-1 home success against Club Atlético Madrid on Saturday. RC Celta de Vigo remain second bottom despite defeating CA Osasuna 1-0 at the Balaídos stadium. Already-relegated Real Murcia CF lost 1-0 at home to UEFA Cup semi-finalists Villarreal CF.
Elsewhere, David Vílla scored four goals for Real Zaragoza in their thrilling 4-4 draw with Sevilla FC at La Romareda. Albacete Balompié won 2-0 at Real Racing Club Santander and Real Betis Balompié edged out Real Sociedad de Fútbol 2-1 at home.