The season's surprise package pounced on Deportivo La Coruna's defeat to Valencia to take command at the top of the table.
The influential Nihat Kahveci proved the difference as the Turkish ace settled the contest after just seven minutes as Sociedad managed to keep the visitors at bay.
Real Madrid bounced back from their Champions League disappointment in majestic style with a convincing thrashing of Malaga at Santiago Bernabeu.
Fernando Morientes set Real on their way after just five minutes with a superb finish and the lead was doubled on 15 minutes by Raul.
Roberto Carlos made it three on 19 minutes before Morientes poached his second on 54 minutes.
Manu pulled one back for Malaga but Raul also helped himself to a brace by rounding off the scoring on 83 minutes.
Villarreal crushed Celta Vigo's Champions League aspirations by taking full advantage of their nine-man opponents to notch a magnificent 5-0 home success.
Celta had been seeking victory to overtake rivals Valencia for the fourth Champions League berth but they are left licking their wounds after the drubbing, in which they contributed heavily to their own downfall.
Both Peter Luccin and on-loan ace Mido were sent off inside 21 minutes, leaving Celta with a mountain to climb to eke something out of the contest.
The visitors held out until 48 minutes when Antonio Guayre (pictured) scored and that prompted the floodgates to open for Villarreal.
Victor was soon on the scoresheet and was followed by Jorge Lopez, Martin Palermo and Guayre again to complete the rout.
Mallorca leapfrogged over Barcelona in the table after a 2-1 success at Camp Nou, where Patrick Kluivert endured an eventful evening.
The Dutch striker put through his own net on 23 minutes but redeemed himself slightly with the leveller on 72 minutes.
But Kluivert's contribution at the wrong end proved crucial as substitute Carlos snatched an 87th minute winner for Mallorca before Barca's Gabri was sent off in injury-time.
Bottom club Rayo Vallecano produced a spirited late fightback to snatch a point at Sevilla and dent their opponents' Uefa Cup aspirations.
Sevilla looked on course for the points when Francisco Casquero and Jose Reyes scored either side of the interval.
Luis Cembranos reduced the arrears with a penalty on 62 minutes but Reyes's spot-kick on 79 minutes appeared to settle matters.
But Rayo delivered a stunning late riposte as goals inside the final five minutes from Michel and Roberto Peragon earned the visitors a precious point in their quest to stave off relegation.
Alaves remain deep in the relegation mire after suffering a 4-2 home defeat to Athletic Bilbao, who boosted their Uefa Cup claims in the process.
Francisco Yeste opened the scoring for the visitors on 20 minutes but Magno and Martin Astudillo put Alaves in control by half-time.
Ismael Urzaiz levelled matters on 57 minutes before Magno was sent off on 71 minutes for his second bookable offence.
Bilbao took maximum advantage of their numerical superiority as Josebe Etxeberria grabbed a brace inside the final 15 minutes.
Osasuna hauled themselves out of the relegation zone after battling back for a 2-1 home win over Real Betis.
Juanito put Betis ahead on 26 minutes but Osasuna were level on the half-hour courtesy of Moha's goal.
Francisco Punal's 39th minute penalty secured the win for Osasuna as Betis ended the match with ten men after Gaston Casas's second-half dismissal.
Valladolid and Espanyol shared the points with Roger's 16th minute equaliser cancelling out Fernando Sales's 13th minute opener for the home side.
Click below for an individual match summary:
Barcelona 1-2 Mallorca
Alaves 2-4 Athletico Bilbao
Osasuna 2-1 Real Betis
Real Madrid 5-1 Malaga
Real Sociedad 1-0 Recreativo Huelva
Seville 3-3 Rayo Vallecano
Valladolid 1-1 Espanyol
Villarreal 5-0 Celta Vigo
