Diego Costa scored the winner for the second game in a row as Chelsea came from behind to beat Watford at Vicarage Road.
Etienne Capoue had put the Hornets ahead on 56 minutes as the hosts looked in control of the game.
But substitute Michy Batshuayi equalised with his first goal for Chelsea since his £33m move.
Then Costa ran on to substitute Cesc Fabregas' pass and slid the ball under Heurelho Gomes with three minutes left.
The win gives Chelsea boss Antonio Conte a 100% start in the Premier League after Monday's victory against West Ham.
Inspired substitutions
Chelsea seemed to be running out of ideas before Conte made his first change on 71 minutes.
Trailing to Capoue's goal, the Blues had had just one shot on target in the match.
But within seven minutes the Italian had rolled the dice and brought on Victor Moses, Batshuayi and Fabregas.
Batshuayi quickly opened his Premier League account just seven minutes after coming in.
He reacted fastest as Heurelho Gomes spilled Eden Hazard's long range into his path and the Belgium forward had a tap-in.
Fabregas, an unused substitute against West Ham, found Costa with a perfectly weighted pass that dissected the Watford defence - and the Spain striker did the rest reports bbc.com.