Real Sociedad pulled three points clear of the relegation zone with a 1-0 win over Espanyol at the Anoeta on Raul Tamudo's reunion with the club.
Ex-Espanyol captain Tamudo joined Sociedad in the summer, and his new side claimed victory via an 85th-minute own goal from Juan Forlin.
The result means Sociedad climb up to 12th in the table, while Espanyol's woeful away form denies them the chance to move level on points with third-placed local rivals Barcelona, who play on Sunday.
Tamudo spent the first 14 years of his career with the Catalan club, over a decade as their talismanic skipper, during which time he scored 129 goals.
However, at 32 years old, and injuries reducing him to just six league appearances last term, Espanyol manager Mauricio Pochettino decided to let his former team-mate leave the club, and he made the short journey to the Basque Country.
Tamudo had a frustrating evening, the tone of which was set when defender Victor Ruiz was booked for a nasty foul on him from behind as early as the eighth minute.
Ruiz then denied Tamudo a close-range finish when he got his boot to a decent cross from Alberto de la Bella just before his erstwhile skipper.
Tamudo's also sent a header right at goalkeeper Carlos Kameni and had another shot from an acute angle parried before being substituted midway through the second half.
Espanyol came into this match on a run of four straight away defeats, and they showed very little attacking ambition until after Sociedad had finally gone ahead.
Substitute Jeffrey Sarpong fired in a well-struck free-kick that Kameni could only tip on to his crossbar. The ball rebounded out and Forlin, aware of two Sociedad players running for the loose ball, tried to flick it away with his heel but succeeded only in knocking it past his own keeper.
Sociedad keeper Carlos Bravo was called into action as Espanyol finally rallied in the final stages, but Sociedad held on for a win that was as deserved as it was vital.
Team Line Up
Real Sociedad
1. Bravo, Claudio | 2. Martinez, Carlos | 3. Gonzalez, Mikel | 7. Griezmann, Antoine | 10. Prieto, Xabi |
8. Callejon | 11. Aranburu, Mikel | 15. Ansotegi, Ion | 17. Zurutuza, David | 19. Rivas, Diego | 20. Tamudo, Raul | 24. De La Bella
RCD Espanyol
1. Kameni, Carlos | 3. David Garcia | 4. Marquez, Javi | 6. Victor Ruiz | 10. Luis Garcia | 11. Verdu, Joan |
14. Galan Inigo, Ernesto | 17. Osvaldo, Pablo Daniel | 18. Forlin, Juan
