Watford piled the pressure on Antonio Conte as a late flurry of goals secured a thumping 4-1 win over 10-man Chelsea on Monday.
On a miserable night for the Premier League champions, the out-of-sorts Tiemoue Bakayoko was sent off after half an hour before Troy Deeney scored the opener from the penalty spot in the 42nd minute.
Chelsea, who were beaten 3-0 at home by Bournemouth in their last game, looked as though they might snatch a point when Eden Hazard scored a brilliant equaliser in the 82nd minute.
But Watford scored three times in seven minutes through Daryl Janmaat, Gerard Deulofeu and Roberto Pereyra to secure victory for new head coach Javi Gracia on his home debut.
While it was a perfect result for Gracia, it is likely to raise even more questions about Conte’s future and how much longer he will remain in charge of Chelsea.
The visitors were under pressure from the start, with Abdoulaye Doucoure dragging a shot wide, Deulofeu shooting into the side-netting and Deeney missing a glorious chance from a corner when he sliced off target.
Willian spurned a good opening at the other end when he fired over from close range, but Chelsea otherwise rarely threatened.
They also lost possession too often, with the main culprit being Bakayoko, who was shown two yellow cards in five minutes and dismissed on the half-hour mark after catching Richarlison.
The first half got worse for Chelsea when Courtois came sliding out and caught Deulofeu in the box. Deeney stepped up and dispatched the penalty with the goalkeeper staying in the middle of the goal.
Watford went close to extending their lead in the second half as Deulofeu and Richarlison both shot narrowly wide.
Chelsea did improve after the introduction of Olivier Giroud and it looked like they might grab a point when Hazard fired in a fantastic shot from 25 yards. But parity did not last long as Watford responded in stunning fashion.
Janmaat made it 2-1 in the 85th minute when he played a one-two, danced away from a couple of tackles and finished into the bottom corner. Deulofeu then fired in from Doucoure’s through ball before Pereyra fired home in injury-time to round off a thumping win.