Madrid:Athletic Bilbao's 1-0 victory over Real Madrid caused the latter to slip five points adrift of Spanish league leader Barcelona, which beat Sevilla 4-0 thanks to Lionel Messi's pair on Saturday.
Athletic striker Fernando Llorente was free in the box in the third minute to head in a corner that was flicked on by Madrid midfielder Lassana Diarra.
Athletic goalkeeper Gorka Iraizoz made key saves on Madrid's big three offseason signings _ Cristiano Ronaldo, Karim Benzema and Kaka _ including a diving stop on Ronaldo's injury-time shot.
Iraizoz made 12 saves in all as Athletic beat Madrid at San Mames Stadium for the first time since 2004.
Barcelona's win at the Camp Nou meant the Spanish champions had 46 points to Madrid's 41 after extending their unbeaten start.
"There's a lot of league left, only one half is (nearly) done," Madrid coach Manuel Pellegrini said. "We won't lack spirit or motivation in our title chase."
Also on Saturday, two early goals gave Osasuna a 2-0 victory over Espanyol to snap a five-game league winless streak.
Following a lackluster first half, Barcelona got on the board in the 49th when Sevilla defender Julien Escude redirected Gerard Pique's shot into his own goal.
Pedro Rodriguez doubled the advantage in the 70th, chipping over oncoming goalkeeper Andres Palop after being played into the area by Xavi Hernandez.
Messi collected Daniel Alves' cross inside the area before slotting a low shot into goal in the 85th.
The world player of the year completed the rout with his league-leading 14th goal in injury time, the Argentina winger breaking into the area alone before tucking back to beat Palop.
Barcelona, which was knocked out of the Copa del Rey by Sevilla on Wednesday, was stronger in the two teams' third meeting in 11 days as the visitors created little offensively to see their league chances likely end following a fourth straight loss.
Sevilla shares 30 points with Mallorca and Athletic. Valencia (35) and Deportivo La Coruna (31) are ahead of them, then Barcelona and Madrid.
At Bilbao, Llorente's header made up for two Athletic misses in the opening moments. Carlos Gurpegui beat goalkeeper Iker Casillas but his low shot hit a post, and Gaizka Toquero then hit the other post from the rebound.
Iraizoz tipped Benzema's swerving shot wide in the 11th as Madrid pressed.
Ronaldo nodded a crossed-in ball high in the air in the 24th and then collided with Iraizoz but the goalkeeper still swiped the looping ball away before it crossed the line.
Benzema, who replaced injured striker Gonzalo Higuain, beat Iraizoz in the 34th but the striker's shot found the far post.
Madrid seemed poised to equalize as Athletic relied on Iraizoz, who stopped long shots from Marcelo and Xabi Alonso before the break.
Benzema unleashed a fierce shot inside the area only to be denied by Iraizoz, who soon after stopped substitute Jose Maria "Guti" Gutierrez's low free kick through the defensive wall.
Iraizoz blocked Kaka's volley in the 69th and the midfielder then half-volleyed a shot from inside the area into the side-netting in the 83rd.
Athletic, which had a penalty appeal waived away during injury time, finished with 10 men when Gurpegui was sent off for a trip on Ramos in the closing stages. Ronaldo sent a free kick over goal in Madrid's final chance.
"There was practically only one team on the field," Pellegrini said. "But you have to have some luck and better precision to convert those occasions. It's clear that when you lose, something's not working."
At Pamplona, Juanfran Torres beat goalkeeper Cristian Alvarez, who was filling in for Carlos Kameni away on African Cup duty, with a low shot in the fifth minute before Walter Pandiani headed home a cross three minutes later.
Osasuna was reduced to 10 men with Roberto "Ruper" Lopez's sending off in the 41st. Facundo Roncaglia wrongly joined Lopez in the stands eight minutes later after the referee showed the Espanyol defender a second yellow even though teammate David Garcia was the one who fouled Carlos Aranda.
Osasuna improved to 20 points while Espanyol had 19.
In Sunday's games, it's: Malaga vs. Getafe; Racing Santander vs. Valladolid; Almeria vs. Tenerife; Zaragoza vs. Xerez; Mallorca vs. Deportivo; Atletico Madrid vs. Sporting Gijon; and Valencia vs. Villarreal.