For a while, Chelsea looked on course for a third straight Premier League loss when Abdoulaye Doucoure and Roberto Pereyra's goals put Watford 2-1 up before Batshuayi and then Azpilicueta instigated the turnaround. Batshuayi added his second in stoppage time.

Chelsea also had the officials to thank after Pedro's opener, a superb long-range strike, came from a corner that should not have been given.

That will be of little significance to Antonio Conte, however, whose relief was palpable when he celebrated Azpilicueta's goal by diving in amongst the Chelsea fans. This was his team's first victory in four matches in all competitions.

They were certainly flattered by the score-line as Watford dominated for large spells and Marco Silva will rue his side's wasteful finishing. Richarlison squandered two excellent chances, the second of which would have put his team two to the good.

Chelsea's victory means they leapfrog Watford in the table, who started the game above their opponents in fourth.

Any early Chelsea nerves were settled by an opening goal that began with a large slice of fortune and ended with a brilliant long-range strike.

Assistant referee Andrew Halliday awarded a corner when the ball clearly came off Hazard's foot last and Chelsea took it quickly, Hazard playing to the edge of the box where Pedro whipped his shot first time off the far post and into the corner.

The champions were temporarily buoyant and Cesc Fabregas should have doubled their advantage when played through one-on-one soon after but his chipped finish plopped into the grateful hands of Heurelho Gomes.

For large parts of the first period, however, Watford were the ones in control and it was no more than they deserved when Doucoure equalised just before the break.

Jose Holebas trundled over from the opposite side of the pitch to launch a long throw into the box and while David Luiz met the header, the ball dropped down for Doucoure to drill in his fourth league goal of the season.

Watford came out all guns blazing and could have scored three in the first 10 minutes. Richarlison missed two sitters, one at the back post, which he side-footed wide and then another with his head, skewing past the far post from five yards.

That should have made it 3-1 because in between Pereyra made no mistake as this time Richarlison turned provider, receiving from Deeney and squaring to his unmarked team-mate to steer past Thibaut Courtois.

Chelsea were on the ropes but Watford failed to land a knock-out blow and later paid the price.

Batshuayi, on for the booked Alvaro Morata, made the difference as he darted across Miguel Britos and headed Pedro's cross into the far corner to pull his side level with 21 minutes left.

Chelsea now looked the more likely to snatch a late winner and Batshuayi almost grabbed it, only to fire over on the turn after a quick free-kick from Fabregas.

But it came moments later. Willian, also off the bench, crossed and Christian Kabasele flicked to the back post where Azpilicueta was waiting to nod in.

There was still time for a fourth in stoppage-time as Britos conceded possession and Batshuayi pounced to round off the victory.