Barcelona crashed to a 1-0 defeat at Real Zaragoza, while Athletic Bilbao beat Valencia.
Zaragoza dominated their illustrious opponents from the start as they took advantage of Frank Rijkaard's decision to play a three-man defence.
They had to wait until the 57th minute to take the lead, Diego Milito (pictured) credited with the goal after getting the slightest of touches to Andres D'Alessandro's acutely angled shot from the byline.
The result leaves Barcelona vulnerable at the top, with nearest rivals Sevilla facing Racing Santander on Sunday.
The second surprise of the night came as Athletic Bilbao claimed a 1-0 victory over Valencia to climb out of the relegation zone.
Igor Gabilondo scored the crucial goal after 28 minutes to keep Valencia in fifth, behind Zaragoza.
Click below for individual match summaries: