Valencia claimed the honorary title of winter champions on Saturday thanks to a 1-0 win at Albacete and a surprise 1-0 defeat for Real Madrid at Real Sociedad.
Valencia, trailing Real by two points at the start of play, clinched victory thanks to a Jorge Lopez penalty after nine minutes.
Real, needing a win to reclaim top spot at the season's halfway point, turned in a dismal display against struggling Sociedad, who secured the points with a Valery Karpin goal after 63 minutes.
With 19 games played, Valencia lead the standings in the Spanish Primera Liga with 43 points, followed by Real Madrid on 42.
Deportivo Coruna, in third place on 36 points and the only other side with a realistic chance of taking the title, will look to close in on Real with victory at home to Racing Santander on Sunday.
Real Sociedad, runners-up to Real Madrid last term but only just above the relegation zone this season, started aggressively and gave their opponents no time on the ball in midfield.
Real, missing the injured David Beckham but otherwise at full strength, hardly created a chance in the opening half-hour, with only Luis Figo causing the home defence any concern with a couple of vaguely threatening runs down the right.
Sociedad gradually strengthened their grip as the game wore on and Darko Kovacevic almost gave them the lead five minutes before the break when he headed Igor Gabilondo's cross over the bar from close range.
Raul had Real's first decent chance early in the second half, the Spain striker forcing a smart save from Alberto after Zinedine Zidane had picked him out in space in the area.
Michel Salgado then volleyed over the bar from the edge of the box but just as the visitors were starting to look dangerous Sociedad took the lead.
Nihat Kahveci, muscling his way down the left, crossed into the middle and Iker Casillas, under pressure from Kovacevic, dropped the ball at the feet of Karpin for a simple tap-in.
Real had plenty of possession in the remaining half-hour but continued to misplace passes and rush their chances when they did come and Sociedad held on for a deserved win.
Valencia were scarcely any better than their title rivals but got the goal they needed when Lopez managed to squeeze a controversial penalty in at Manuel Almunia's right-hand post after Pablo Aimar had gone down on the edge of the box.
Albacete had plenty of chances to equalise but Valencia keeper Santiago Canizares pulled off a couple of outstanding saves as the visitors held on.