Villarreal lost ground to Athletic Bilbao in their bid to finish fourth as they were held to a 1-1 draw at home to bottom side Real Betis.
The hosts looked set to take all three points when Bruno Soriano gave them the lead from the penalty spot on 70 minutes, but the game changed 10 minutes later when Uche Ikechuwku was sent off for a second booking.
Betis then took advantage of having an extra man, Ruben Castro heading in the equaliser shortly after.
The point does little to help Gabriel Calderon's side's plight - the Andalusians are 11 points from safety and still face a gargantuan task if they are to avoid the drop - and is a blow to Villarreal, now six points behind fourth-placed Athletic.
A solitary goal by Joaquin Larrivey gave relegation-threatened Rayo Vallecano all three points against Valencia, moving the Madrid side to within three points of safety.
The Argentinian striker headed in the only goal of the game on 61 minutes and Valencia were dealt a further blow when Antonio Barragan was sent off a quarter of an hour later for picking up a second booking.
Rayo remain 19th in the table but have closed the gap on 17th-placed Almeria to three points, while Valencia suffered their first defeat in six matches and drop down to 9th.
Substitute Kevin Gameiro's second-half strike was all that separated the teams as Sevilla claimed a 1-0 victory over Real Sociedad at the Ramon Sanchez Pizjuan.
Gameiro struck after 77 minutes to end Sociedad's two-match winning run as Unai Emery's Red and Whites moved up a place to seventh.
