David Coote is the on-field referee for this encounter and Darren England his VAR.
Chelsea: Mendy, Chalobah, Christensen, Rudiger, Azpilicueta, Loftus-Cheek, Saul, Alonso, Pulisic, Mount, Havertz. Subs: Kepa, Jorginho, Silva, Lukaku, Werner, Barkley, Hudson-Odoi, Ziyech, Sarr.
Watford: Bachmann, Femenia, Cathcart, Troost-Ekong, Masina, Louza, Joao Pedro, Cleverley, Sissoko, King, Bonaventure. Subs: Ngakia, Rose, Gosling, Fletcher, Tufan, Kabasele, Hernandez, Kucka, Elliott.
Hello and welcome to our blow-by-blow coverage of this Premier League clash between Watford and table-topping Chelsea at Vicarage Road.
KICK-OFF! Chelsea get the match underway at Vicarage Road.
Cleverley beats Alonso on Chelsea's left and cuts back for Joao Pedro, whose shot is blocked by Chalobah. Watford have started well.
Joao Pedro has a chance from close range, but Mendy makes a fine save!
Play has been paused. We will get more information to you as we find it out.
Play is back underway with Masina replaced by Rose. Masina was receiving medical attention before the game was delayed.
It appears the situation has been resolved and the players are going through a five-minute warmup before restarting.
There has been a medical emergency in the crowd, it seems.
Saul fouls Bonaventure right outside the box. This is within shooting range for Watford.
Louza fires the free-kick into the wall and then drags his follow-up shot well wide of goal.
POST! Loftus-Cheek sets up Mount, who hits the upright. Saul can't capitalise.
Chelsea are only now beginning to find a bit of rhythm, having been outplayed in the first quarter of an hour.
Chelsea are still looking sloppy in possession, giving the ball away far too cheaply.
GOAL, CHELSEA, MOUNT! 0-1: Chelsea work the ball beautifully. Rudiger plays the ball over the top for Alonso, who cuts back for Havertz, who tees up Mount for a beautiful finish!
Saul wins the ball in midfield. Pulisic comes away with possession and slips Mount in. The German scores, but the flag is up for offside against him.
Chelsea's failure to properly clear the ball leads to a Rose chance at the far post. Mendy gets down to make a superb save off a stinging shot!
GOAL, WATFORD, BONAVENTURE! 1-1: Wonderful run from Bonaventure before he smashes home the equaliser.
HALF-TIME: WATFORD 1-1 CHELSEA. The teams head into the break all square after a pulsating first half.
Silva is on in place of Saul for Chelsea. The second half is underway.
Chelsea begin the second half on the front foot, looking to apply pressure. Pulisic takes too long to shoot before teeing up Mount, whose shot is blocked.
Watford look to hit Chelsea on the break with Mendy coming out to smother Cleverley. The two players collide, with Chalobah also looking worse for wear.
Ziyech is on in place of Chalobah, who picked up an injury.
Romelu Lukaku appears to be set to come on shortly for Chelsea as they look for a late winner.
Louza receives the ball from Joao Pedro and goes for goal, firing off target.
Ziyech finds Havertz, who beats a couple of Watford defenders and fires for goal. Troost-Ekong appears to get a block in and it's ultimately no problem for the goalkeeper.
Azpilicueta makes way, giving the armband to Rudiger, with Lukaku coming on.
GOAL, CHELSEA, ZIYECH! 1-2: Mount's low cross from Chelsea's left finds Ziyech, who strokes home effortlessly to put Chelsea back in front!
Kucka is on for Watford in place of Louza.
Tuchel continues to demand more of his players from the sidelines. Lukaku is flagged offside.
Lovely counter from Chelsea following a Watford attack. Havertz's perfectly weighted ball finds the head of Ziyech, but his effort at goal is saved this time.
Ngakia is on for Watford in place of Cleverley. Rose picks up a yellow card for a foul on Ziyech. Cleverley has also seen yellow.
We are into six minutes of stoppage time. This game is not over yet by any means.
Kucka goes for goal from a Watford free-kick. His shot is powerfully struck, but Mendy tips behind.
FULL-TIME: WATFORD 1-2 CHELSEA. Goals from Mount and Ziyech have led Chelsea over the line as they stay top of the table. Thomas Tuchel will be the first to recognise that in order to win the league, they have to play better than that.