The Hornets started energetically, much like they did against Manchester United and Leicester City, forcing Edouard Mendy into a string of good saves. The stop of a possible Cesar Azpilicueta own goal was a particular highlight.
It was, however, the league leaders who opened the scoring. Mason Mount stroking the ball into the net from six yards out after he had hit the crossbar a couple of minutes prior.
Watford kept up their pressure and were rewarded late in the first half with Emmanuel Dennis scoring his sixth of the season to draw them level. Moussa Sissoko had another chance for Watford in added time to give Claudio Ranieri's men the lead but was unable to take advantage.
In the second half, Watford continued to pile on the pressure but it was Chelsea who took the points a little over 15 minutes from full-time. Hakim Ziyech proving the difference as scored his first Premier League goal of the season.
Here are the three key takeaways from an entertaining encounter at Vicarage Road.
Watford unfortunate not to get more
Since Claudio Ranieri took charge of the Hornets, his side had begun to play a more optimistic style of football, taking the game to their opponents.
"Ranieri-ball" has seen Watford's two victories under his belt be 5-2 and 4-1 wins against Everton and Manchester United respectively. As that implies, two wins from six prior to Chelsea (W2 L4) does not sound too positive. But it has been better than it seems, and hosting the Blues was to prove no different.
Realistically, Ranieri's men should have earned themselves a point. Chances from Moussa Sissoko and Danny Rose frightened the away side, and at one point it looked like there could be a shock result on the cards.
Since the international break, Watford may have only taken points against Manchester United - but each performance has been admirable. A 4-2 defeat at Leicester City was only down to dire defending, and the 2-1 defeat on Wednesday evening was unlucky still.
Indeed, the Hornets' attack will be something most teams envy. 19 goals scored in 14 games is fewer than only seven teams. Their defensive record, however, has seen only Norwich City and Newcastle United concede more.
Watford's high press - something first witnessed at Everton, before being seen ever since the international break - is paying dividends. The first half was dominated by Chelsea slip-ups and Watford dominating the play in front of the Rookery Stand.
Ranieri is turning the Hornets into a formidable attacking force, with Chelsea fortunate to escape with all three points.
Dennis the Menace
Emmanuel Dennis, a cheap summer signing from Club Brugge, has proved to be something of a revelation. With his sixth goal of the season against the Blues, he has now taken his goal contributions to 11 for the season. Only Mohamed Salah has contributed more.
The Nigerian international is evidently playing on a wave of confidence. A clever goal against Leicester was replicated under the lights, Dennis dribbling inside and finding the net, albeit helped by a slight deflection.
Finding the space and making clever runs nearly saw him find his sixth assist of the season - again cutting inside before putting Sissoko through.
Alongside the sidelined Ismaila Sarr, Dennis has rejuvenated the Watford wings, providing a burst of pace and - together with Joshua King up front - is making quite the difference in the Hornets' goal-scoring fortunes.
With 0.73 goal-creating actions per game, Dennis has one of the highest rates in the Premier League. At times, the very tough Chelsea defence seemed battled to quell him.
Ranieri is bringing out the best in him. Dennis is no doubt a superb asset to Watford and has gone very much under the radar - probably to his liking.
Chelsea continue racking up points
Although Watford deserved more, Chelsea continue picking up points.
Despite being unable to pick up his ninth clean sheet of the season, he denied what looked like a certain Azpilicueta own goal; got down fast to deny Rose; and rushed out to deny Cleverley. His broad style of play is giving the attack more to work with.
That attack has seen Chelsea score the second most goals in the league this season, only behind Liverpool. Against Watford, they took every opportunity which came their way. Mason Mount dominated the forward line, contributing to both goals.
Whenever Chelsea came forward on Wednesday they threatened. Although Watford may have dominated much of the play, silk play from the opposition when pressing forward meant the hosts' defence could not cope.
It will no doubt help Chelsea when Jorginho returns to the outfit. On a few occasions they lost the ball in the midfield area and looked susceptible to a counter-attack, especially in the first 45 minutes.
In the end, it did not matter, and Chelsea continue to look like title-contenders. It will take a tough task for many teams to beat them this season, with only Pep Guardiola's Manchester City managing that so far.
They will hope to continue their dominance at the head of the Premier League against a high-flying West Ham United in Saturday's early kick-off. Meanwhile, in the late kick-off, Watford will have to be in their finest form to take something off Man City.