Chelsea's win over West Brom on Friday night confirmed them as English champions for the sixth time, and fifth in the Premier League era.
Outgoing John Terry as well as Michy Batshuayi, Cesc Fabregas and Cesar Azpilicueta all hit the scoreboard, pipping Watford in the 88th minute of the game.
Blues skipper John Terry, who will leave the club at the end of the season, scored the opener in his 716th game for Chelsea.
It proved to be the appetiser for a insane 90 minutes of football as the home side threw away a 3-1 lead after Daryl Janmaat and Stefan Okaka cancelled out other efforts from Cesar Azpilicueta and Michy Batshuayi.
And substitute Stefano Okaka equalised after holding off Terry before Fabregas' decisive 88th-minute strike.
Watford finished the game with 10 men after centre-back Sebastian Prodl received a pair of late yellow cards for untidy challenges on Batshuayi and Pedro.
However, Terry, capped 78 times by England, admitted Sunday's home game against relegated Sunderland - where a win would see Chelsea become the first Premier League champions to win 30 games in a 38 match campaign.
For sure, for us, this is a big loss next season. "History has proved it's very tough to win it back-to-back, but it has to be a target for us next year, 100 percent", Cahill said. "I think the FA Cup final, you don't play that on Saturday".
The party atmosphere went quiet within seconds of the restart, however, when Terry failed to clear a cross in front of the Chelsea goal, heading the ball up rather than out of the danger area and giving Etienne Capoue the simplest of tasks to equalise.
"I think if you compare Tottenham Hotspur with Chelsea, they had an advantage this season", the Italian manager told The Guardian. "You start to plan ten days before". "It's good to play against Watford again and they played a good game".
Chelsea boss Antonio Conte feels he can have few complaints after a much-changed side, containing a number of young players, edged out Watford 4-3 at Stamford Bridge this evening.
"I was sitting there wishing that the boys kept winning and performing well because for me I have had my time".