Oscar Garcia has resigned from his position as Watford manager and has been replaced by Billy McKinlaySpaniard Garcia, 41, spent a week in hospital earlier this month after suffering from chest pains and only returned to the Hornets training ground late last week.
He watched Saturday's 2-2 draw at Blackburn from the directors' box but has now decided to hand over the reins to McKinlay, who was added to the Watford coaching staff last week.
Watford say that while Garcia's health is of no further cause for concern, he requires rest and has decided it is in the club's interest that he stands aside.
The former Brighton boss only took over at Vicarage Road on September 2 and was in charge for just one match, a 1-0 defeat at Charlton, before being admitted to hospital.
"I was closely involved with the appointment of Billy McKinlay, because I was aware that I may not be able to return," Garcia told the club's official website.
"I always wanted an experienced British coach within our set-up, because it's important to have that mix of cultures and experience with this squad.
"I would like to thank Watford's fans for their kindness during my time here at the club. I will be hoping to see you all as a Premier League club next season."
McKinlay, 45, is expected to continue in his role as Northern Ireland assistant manager for the time being.
The Scot's first game in sole charge of the Hornets will be at home to Brentford on Tuesday night.
Watford CEO Scott Duxbury said: "Everyone feels it is important that there is continuity in the coaching structure. Ruben Martinez and Javier Pereira will therefore continue as Billy McKinlay's assistants.
"We appreciate Oscar's candour in placing the best interest of Watford FC ahead of his own personal thoughts and we wish him well for his future in football.
"In Billy McKinlay, we have someone with the qualities and significant experience to build further on the foundations already laid for a successful season ahead."