Gary Neville is still without a league win as Valencia manager after two goals from Brazilian striker Jonathas gave Real Sociedad victory.
Jonathas scored twice in three minutes in the second half to condemn Neville to defeat in San Sebastian.
The former Manchester United and England defender has two losses and three draws in La Liga.
His team face struggling Rayo Vallecano and mid-table Deportivo La Coruna in their next two league games.
Neville’s only two wins in charge so far have come in the Copa del Rey but he looked to be heading for an away draw until Jonathas opened the scoring from close range in the 79th minute.
The striker then doubled Sociedad’s lead with a powerful header three minutes later.