Quique Sanchez Flores' return to Watford was confirmed just 20 minutes after the sacking of Javi Gracia.
The Spaniard was out of work after after leaving Chinese side Shanghai Shenhua earlier this summer following a short stint in charge.
The 54-year-old was a popular figure at Watford's Hertfordshire training complex following his one season in charge at the club during the 2015/16 campaign.
Flores was a popular figure at Vicarage Road during his one season in charge of the club
He led the team to an FA semi-final and a comfortable mid-table position in their first season back in the top-flight after promotion.
The Daily Mail says it is understood Gracia maintained the backing of the majority of his playing squad - while there is acknowledgement that Troy Deeney's absence due to injury has hampered the team's chances.