Cesc Fabregas earned Chelsea a thrilling 4-3 victory against Watford in their first match since they clinched the Premier League title.
His first-time strike from Willian's pass earned three points after Watford staged a comeback from 3-1 down.
John Terry led Chelsea out to a guard of honour from Watford, and he put the Blues in front with a close-range finish before his mistake allowed Etienne Capoue to head in a quick leveller.
Cesar Azpilicueta's drilled effort made it 2-1 at half-time before Michy Batshuayi, who scored the goal that won Chelsea the league at West Bromwich Albion, added a third.
A brilliant solo goal from Daryl Janmaat and Stefano Okaka's hit put Watford on level terms before Fabregas's late winner and a red card for Sebastian Prodl in stoppage time.
See: Chelsea report | Watford report