Real Sociedad came down to earth with a bump as local rivals Eibar beat them 2-1 in the Basque derby.
Sociedad's previous two games had brought them wins over Sevilla and Barcelona, but Eibar joined them on 41 points with a first win in nine games almost certainly securing their Primera Division safety.
Sergi Enrich and Gonzalo Escalante were on target as Eibar, promoted in 2014, won a top-flight fixture for the first time after trailing.
David Zurutuza gave the visitors a seventh-minute lead with a quite brilliant effort, his first goal of the season.
Zurutuza lifted the ball over Danny Garcia after taking possession from a throw-in and volleyed it into the far corner of the net from 18 yards.
Carlos Vela should have doubled the lead but his weak chip travelled tamely wide and Sociedad were punished after 32 minutes.
Ander Capa's cross picked out Enrich and the striker's header took a crucial deflection off Diego Reyes to beat Sociedad goalkeeper Geronimo Rulli.
Markel Bergara almost restored the lead when his header was brilliantly saved by Asier Riesgo and Xabi Prieto's effort was disallowed for offside.
Eibar's winner came after 58 minutes when Zurutuza carelessly gifted possession to Enrich and his cross evaded Rulli for Escalante to squeeze his header past two defenders.
Keko and Escalante might have settled it for Eibar, the latter striking the crossbar from a tight angle, but Sociedad felt they should have had a penalty when Vela was felled in stoppage time.
ends