Hayden Mullins will take charge of Watford’s Premier League game away to Leicester on Wednesday, following the sacking of Quique Sanchez Flores.
The U23s coach, who played for Crystal Palace and Portsmouth during his career, oversaw training alongside head of academy goalkeeping Graham Stack on Monday morning.
Watford suffered their eighth league defeat in a 2-1 loss against Southampton on Saturday, which saw them remain bottom of the table on eight points and six adrift of safety - their worst return at this stage of a Premier League campaign
Sanchez Flores was sacked 85 days after he was re-appointed for a second spell at the Premier League club on Sunday, with the appointment of a successor described then as imminent.
The club said ultimately results have dictated our decision to dispense with a second head coach this season, after Javi Gracia was sacked in September, four games into the league campaign.
A new head coach is not expected to be announced until Thursday at the earliest, after the club`s original intention to appoint a quick replacement has since changed.
Former Brighton and Newcastle boss Chris Hughton was one of the leading candidates, but at this stage it looks like that is no longer the case, while ex-Swansea manager Paul Clement was also considered.
Sanchez Flores returned to the club`s training ground on Monday to say goodbye to members of staff.
Watford, who are in their fifth season back in the top flight, host Crystal Palace at Vicarage Road on Saturday after the visit to Brendan Rodgers` Leicester in midweek.