Real Sociedad stretched their impressive run of results to just one defeat in 11 league games but were unable to make their numerical advantage count as 10-man Celta Vigo held on for a 1-1 draw at Balaidos.
Michael Krohn-Dehli had given the hosts the lead with a wonderfully worked goal after 32 minutes but Celta were forced onto the back foot just after the break when Augusto Fernandez received a second yellow card for a handball.
Gorka Elustondo then brought Sociedad level with a powerful header from Gonzalo Castro's corner just before the hour mark, but the visitors failed to create many more clear-cut chances in the final half an hour and remain five points off the top four.
Indeed chances were few and far between all day as neither side showed the slick passing football that they have on many occasions so far this season.
Sociedad were first to go close 22 minutes in when Carlos Martinez's cross from the right found Diego Ifran completely unmarked inside the box, but the Uruguayan pulled his shot past Javi Varas' right-hand post.
Claudio Bravo then had to turn away an effort from Fernandez at the other end as Celta awakened and they took the lead moments later with the one real moment of quality in the game as Krohn-Dehli was fed by an impotent backheel from Aspas and drilled his shot low past Bravo from inside the area.
The Chilean keeper then had to be alert to stop Krohn-Dehli adding a second with a fierce drive from outside the area just before half-time, but the hosts were dealt a huge blow when Aspas did not return to start the second-half as he had to be replaced by Alex Lopez due to a back injury.
Paco Herrera's men's task then got even tougher as Fernandez was somewhat harshly shown a second yellow for handling four minutes after the restart, and it took the visitors just 11 minutes to take advantage as Elustondo rose highest to power in his first goal of the season.
Thereafter Sociedad probed as Celta sat back and tried to hold on to what they had, but apart from a long-range effort from Markel Bergara that hit the outside of the post and an Antoine Griezmann header that flew just wide in stoppage time, Philippe Montanier's men did little to threaten Varas' goal.