Villarreal suffered their first defeat since returning to the Spanish top-flight on Sunday as Nosa Igiebor's first-half goal handed Real Betis a 1-0 win.
The Nigerian midfielder pounced nine minutes before half-time to steer the ball home after Villarreal keeper Sergio Asenjo had parried Joan Verdu's effort.
Villarreal pressed for an equaliser after the break, but it was Betis who looked more likely to score again on the counter-attack and Asenjo did brilliantly to deny Verdu when he was played clean through on goal by Jorge Molina seven minutes from time.
The visitors' miserable evening was rounded off when manager Marcelino Garcia Toral was sent to the stands in stoppage time for dissent after the referee only gave a corner when Villarreal thought Javier Aquino had been felled inside the area.
Defeat meant Villarreal miss the chance to leapfrog Real Madrid into third place and they could be out of the top four by Monday evening should Athletic Bilbao beat Granada.
Earlier, Elche secured their first win in the top-flight for 25 years as they won 1-0 away at Celta Vigo.
Javi Marquez scored the only goal of the game with a low angled drive from Carles Gil's headed pass just after the hour mark.
Espanyol missed the chance to move back into the European places as they suffered their second defeat in four days in a 2-0 reverse at home to Getafe.
Adrian Colunga scored both goals for the visitors in the second-half to secure Luis Garcia's men's first away victory of the season.
And in the day's early game Levante won 1-0 away to Osasuna thanks to Jordi Xumetra's goal two minutes from time as he swept home the rebound after Andres Fernandez had save Pape Diop's penalty.