Valencia fired coach Albert Celades on Monday after a run of bad results culminated with a defeat by the La Liga club's bitter local rivals Villarreal at the weekend.
Valencia have picked up a meagre four points from a possible 15 since the restart following the coronavirus lockdown, dropping to eighth in the league, eight points off the Champions League qualifying spots.
"Valencia have informed Albert Celades of his immediate release," a club statement said.
Former caretaker coach Voro has been called in again as a temporary replacement for the sixth time.
Celades took over at the Mestalla last September after the surprise sacking of previous boss Marcelino, who had led the club to back-to-back fourth-placed finishes.
But Celades has failed to last the season after Sunday's 2-0 loss at Villarreal left Valencia with just two wins in 13 matches in all competitions.
Valencia were also knocked out of the Champions League by Atalanta in March after an 8-4 aggregate defeat in the last 16.