The Blues came back from behind to win for the first time this season, moving them up above their opponents and into fourth place.
Michy Batshuayi took advantage of a misplaced defensive header and used his considerable bulk to hold off Miguel Britos to slot in the fourth goal.
Chelsea right-back Azpilicueta pops up at the left-hand post to meet a peach of a cross from Willian, guiding a downward header past Heurelho Gomes at the 87th minutes to get the third goal.
Chelsea had the first goal of the match in the 12th minutes through Pedro, but Watford striker Doucouré level the margin in (45’+2minutes), close to the halftime.
Watford took the lead just as the second half resumed with a striking goal from Pereyra in the 49′ minutes
At game over it was, however, Chelsea’s day at Stamford Bridge with the 4-2 match result