Watford announced that Marco Silva had been relieved of his duties, just seven months after the joining the Hornets from Hull City.
The Portuguese coach was approached by Everton to replace Ronald Koeman earlier this season - and Watford's results have suffered since.
The club statement, posted less than 24 hours after the 2-0 loss to Leicester City - did not thank Silva, or wish him well, but did lay the blame of his failure on Everton's doorstep.
It read as follows: “The Club is convinced the appointment of Silva was the right one and had it not been for the unwarranted approach by a Premier League rival for his services we would have continued to prosper under his leadership.
“The catalyst for this decision is that unwarranted approach, something which the Board believes has seen a significant deterioration in both focus and results to the point where the long-term future of Watford FC has been jeopardised."
Silva had signed Richarlison in the summer and the young Brazilian winger has been a revelation at Vicarage Road.
"We analysed him [Richarlison] for some weeks in June, when he was playing in Brazil. We took the decision to tell the board to do everything we could to sign the player," said Silva in November.
The 40-year-old coach has ostracised players like Stefano Okaka and Étienne Capoue but clearly had a close relationship with Watford's star man.
Richarlison's tweet after Silva is sacked
The skilful 20-year-old, who has already been linked with a move to Arsenal and Chelsea, was the first Watford player to react to Silva's somewhat surprising dismissal.
He just tweeted an emoji but Watford fans were not happy about it at all.
How Watford fans reacted
If Richarlison wasn't already certain to leave in the summer, he is now.
Former Malaga and Rubin Kazan boss Javi Gracia was appointed Watford's new manager on Sunday evening.
He signed an 18-month contract and will face Southampton in the FA Cup fourth round in his first game in charge.
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