It shouldn't have been that way – that's what Blues fans will think at least. After their side had gone in front through a sumptuous goal from Pedro, the afternoon should've been straight forward.
But Marco Silva's Watford are made from stronger stuff. Some may even say they have cojones. They equalised on the half hour through Abdoulaye Doucouré before going in front in the second period via Roberto Pereyra.
And then came a turning point. With Watford on top, Miguel Britos crossed and Richarlison was left unmarked six yards out. The Brazilian had already missed a gilt-edged chance and repeated the trick as he directed his header wide.
From that moment Chelsea improved and equalised when Michy Batshuayi glanced a header past Heurelho Gomes. With the home side on top, César Azpilicueta then nodded Antonio Conte's side in front.
Batshuayi added an undeserved fourth in stoppage time to make the scoreline harsh on Watford. And here are three big questions raised by the game.
Will Chelsea's Win Paper Over The Cracks?
There would've undoubtedly been a feel-good factor among the Blues fans leaving Stamford Bridge at full time. Their side had scored four goals and shown character to come from behind and beat a spirited Watford team.
But when the feeling of euphoria dies down, Chelsea supporters will know this victory is one that wasn't truly deserved. Had the Hornets, and more specifically Richarlison, taken their chances then the game would've been over with 20 minutes to play.
Chelsea were fortunate. Defensively, especially in the first 20 minutes of the second period, they were all over the place. The two wing-backs were constantly caught upfield while David Luiz, Antonio Rüdiger and Gary Cahill struggled with the movement of Watford's front three.
The lack of protection from the midfield two of Cesc Fàbregas and Tiémoué Bakayoko was also a factor and is a big issue for Conte with N'Golo Kanté set to remain on the sidelines for another fortnight.
Chelsea have kept just four clean sheets in 14 games this season, that is not good enough and suggests opposing sides have worked out how to attack Chelsea's three-man defence.
Roma were unfortunate not to leave Stamford Bridge in the week with three points. Watford can now feel hard done by too. At some point, Chelsea's luck will run out unless Conte can solve several issues in his side.
When Will Doucouré Be Linked With A Big Move?
On August 31 2016, Abdoulaye Doucouré was set to leave Watford on loan. He wasn't in the then-head coach Walter Mazzarri's plans and wanted to go out and play first-team football.
Ligue 1 side Lorient were ready to offer Doucouré an season-long escape route by signing the midfielder on loan. A deal was agreed and the Frenchman travelled to Luton Airpot to fly out and complete a move.
Then a phone call came. The deal was off, Doucouré would remain at Vicarage Road as there was no time to complete a deal. It would prove to be a blessing in disguise for the player and Watford.
It took a while but Doucouré would win over Mazzarri and impressed during the second half of last season as the Hornets faltered. This term, under the guidance of the impressive Silva, Doucouré has elevated his game and is now one of the finest box-to-box midfielders in the Premier League.
Doucouré has the lot. Power, pace, energy and no little technique. And he demonstrated that against Chelsea.
His first half was virtually flawless. In addition to his equalising goal, the 24-year-old former Rennes man completed 97.5 per cent of his 45 passes and also made three interceptions.
His goal was excellently taken, too. It was the fourth time in the Premier League this season Doucouré has found the back of the net, and he's only had four shots on target.
Given his performances at the heart of the Watford midfield you sense it won't be too long until Doucouré is linked with a big money move away from Vicarage Road.
For instance Chelsea, who were without Kanté due to injury, could've certainly done with someone of Doucouré's ilk in the heart of their midfield.
But for now he is a Watford star, and one Hornets fans must enjoy on and on…
Has Batshuayi Saved His Chelsea Career?
After a dismal showing against Crystal Palace last weekend, the Belgian's future at Stamford Bridge looked bleak.
At Selhurst Park Batshuayi's movement was poor, he couldn't hold up the ball and, to be blunt, he looked out of his depth against the worst side in the division.
But what a difference a week makes. Introduced from the substitutes' bench against in place of Álvaro Morata, the 24-year-old had 29 minutes to make an impact. He certainly did that.
In less than half an hour on the pitch, Batshuayi had four shots on goal, two of which were on target and both found the back of the net. He helped turn defeat into victory.
As a substitute Batshuayi can be an effective option to turn to when things aren't going Chelsea's way. He, when on form, brings a very different approach to the more nuanced Morata and that can be vital.
The big question mark remains as to why he fails to perform when given a start. A lack of match fitness? Perhaps. Given his persona, you doubt it is down to a lack of confidence.