Osasuna joined Real Madrid at the top of the Primera Liga on Sunday after second half strikes from Savo Milosevic and Pierre Webo secured the Navarrans a 2-0 win at home to Celta Vigo.
Milosevic broke the deadlock in a delicately balanced game against his former side when he curled a pin-point strike past Celta keeper Jose Manuel Pinto from just outside the box in the third minute of the second half.
Cameroon striker Webo made it 2-0 seven minutes from time when he raced on to a through pass after a lightning counter attack from inside the Celta half, slipped the ball past Pinto and guided the ball into the empty net.
The win left the Navarrans in second place in the table, level on 15 points with Real who beat city rivals Atletico Madrid 3-0 at the Calderon on Saturday.
Former leaders Getafe lost their unbeaten record when they went down 1-0 at Real Betis and are now a point behind in third place while Celta have dropped to fourth.
Brazilian striker Ricardo Oliveira scored the Betis winner on 17 minutes when he smashed a penalty into the roof of the net after keeper Luis Garcia was harshly adjudged to have brought the striker down as he raced into the area.
Getafe's misery was compounded by midfielder Diego Rivas being sent off after a second booking a minute from time.
Valencia moved up to fifth place, a point behind Celta and three behind leaders Real after a 2-1 win at home to Malaga.
Argentine centre-back Roberto Ayala put the home side ahead when he snapped in a shot from six metres out after a Miguel Angel Angulo corner in the 10th minute and midfielder Vicente made it 2-0 when his deflected shot ballooned over keeper Francesc Arnau and into the net midway through the second half.
Real Zaragoza, the only other side who had not lost a game ahead of this weekend's matches, slumped to their first defeat when they went down 1-0 at home to Real Sociedad.
Midfielder Xabi Prieto scored the winner from the penalty spot in the 12th minute after Zaragoza defender Alvaro was adjudged to have pushed striker Gari Uranga in the area.
Sociedad lost midfielder Mikel Aranburu 18 minutes from time after picking up a second yellow card for a foul on Leonardo Ponzio, but the Basques held on for a valuable away win.
Sociedad are now in eighth place in the standings level on 10 points with Barcelona and Deportivo Coruna who drew 3-3 at the Riazor on Saturday.Cadiz secured their second win since returning to the top flight with a thoroughly deserved 2-0 victory at Espanyol thanks to well taken second half strikes from midfielders Matias Pavoni and Jonathan Sesma.