Bottom-placed Osasuna have slumped to their sixth defeat of the season as a late Patrick Ebert goal earned Real Valladolid a 1-0 win at the Estadio El Sadar.
The home side carved out the better openings in the first half, with Alvaro Cejudo firing off target twice.
However, their chances of getting anything from the match were dealt a blow in the 76th minute as Ruben was sent off for picking up his second yellow card of the night.
The numerical difference worked in Valladolid's favour when Ebert chipped Andres Fernandez with seven minutes to play to seal the three points for the visitors.