Two games, two late wins gives by Diego Costa, 6 points and a +2 goal difference that give them the fourth place in the table.
After a first half poor of emotions and chances, Watford took the lead at minute 55 with a goal by Etienne Capoue.
Chelsea, however, was always in control of the game and the hard work paid at minute 80 when Michy Batshuayi, entered 7 minutes before to replace Oscar, picked up a loose ball and equalised.
After seven minutes, Diego Costa scored another late winner after the one of last Monday night against West Ham, and gave other three points to Chelsea: Cesc Fabregas provided the assist.
Another crazy celebration for Antonio Conte, and another self confidence and enthusiasm injection for Chelsea.
Watford 1-2 Chelsea
Capoue 55 Batshuayi 80 Diego Costa 87
Chelsea: Courtois; Ivanovic, Cahill, Terry (c), Azpilicueta; Kante; Pedro (Moses 71), Oscar (Batshuayi 73), Matic (Fabregas 78), Hazard; Diego Costa
Other subs: Begovic, Aina, Loftus-Cheek, Chalobah.
Watford: Gomes; Cathcart, Prodl, Britos; Amrabat, Behrami, Capoue (Doucoure 84), Guedioura (Vydra 89), Holebas (Zuniga 90); Deeney (c), Ighalo
Watford (3-5-2): Gomes; Cathcart, Prodl, Britos; Amrabat, Behrami, Capoue (Doucoure 84), Guedioura (Vydra 89), Holebas (Zuniga 90); Deeney (c), Ighalo.
Other subs: Pantilimon, Nyom, Anya, Hoban.
Bookings: Cahill 20, Diego Costa 56, Hazard 90+2 Deeney 19, Britos 69, Holebas 70, Behrami 90+4