Watford sacked Javi Gracia on Saturday and appointed Quique Sanchez Flores in his stead.
Sanchez had coached Watford in 2015-16 and then left at the end of the season.
Watford are currently bottom of the league with only one point from their first four games.
Garcia took them to the FA Cup final last season but they lost 6-0 to Manchester City.
Watford chairman Scott Duxbury said: "Javi has represented Watford with great dignity and will always be deserving of our fullest respect for his achievements."