The Argentine coach won the title twice as a player with Los Che, but finds himself carrying the can for their fall in form.
Pellegrino the fall guy for Valencia's decline in fortunes
Valencia had the second-best away record in Spain a year ago. Today they have the worst, with no wins from seven matches and just two goals scored. They are 12th in the Primera Liga table.
Last December, Los Che sat third, a position they would finish in for the third successive year under the coach Unai Emery.
Given the dominance of Barcelona and Real Madrid, it was implausible that Valencia could do any better, yet it was not enough for fans who had seen their side win the league in 2002 and 2004, plus reach consecutive Uefa Champions League finals in 2000 and 2001.
They were not always realistic about how the dynamics of Spanish football had changed in favour of the biggest two clubs - Barcelona and Real Madrid - and not Valencia.
Yet Valencia, despite being in debt and twice facing extinction, continued to thrive under Emery despite selling their best players season after season.
Top-class performers such as David Villa, David Silva, Juan Mata and Jordi Alba left the club - and still they finished third last season.
The one asset they could not sell was their famous, sheer-sided Mestalla home, located in a prime area close to the centre of Spain's third-biggest city. The sale was vital to funding their new, 75,000-capacity home, but when Spain's economic crisis hit in 2009, the construction had to stop and Valencia were left in the lurch.
Emery continued to succeed, but it still was not enough. He was dismissed at the end of last season and replaced by the former defender, Mauricio Pellegrino, the Argentine who was twice a title winner with Valencia as a player.
Pellegrino lost his job after Valencia were heavily beaten 5-2 at home on Saturday by Real Sociedad.
The fans who had booed during the game demanding a change got one, just not the one they wanted. Despite the team's poor form, they still supported Pellegrino.
Instead, they chanted for the president Manolo Llorente's head. He has heard dissenting fans many times before and stuck by several coaches, but he reacted to fans calling for him to go by sacking his coach.
Pellegrino did not approve, saying it was an "unfair decision" which had been taken "in the heat of the moment", but his record at Valencia is up for scrutiny and there are rifts in the dressing room. The Spanish manager Ernesto Valverde is Pellegrino's replacement.
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