Watford went toe-to-toe with Chelsea and although they came off second best with the Premier League leaders in a 2-1 defeat at Vicarage Road tonight, the way in which they set about the task and the performance they produced should give them plenty of encouragement for the busy month ahead after the game had to be halted for a medical emergency.

A second-half strike from Hakim Ziyech ultimately proved the difference after Emmanuel Dennis had cancelled out Mason Mount’s opener, but the Hornets pushed their opponents all the way and were the better side for large parts of it.

The Hornets started positively, pressing very high as they sought to impose themselves on Chelsea, but the game had to be halted in very concerning circumstances due to a medical emergency in the Upper Graham Taylor Stand.

The contest was halted for at least 25 minutes after stewards and medical staff from both clubs and inside the ground rushed to the aid of a fan who had suffered a cardiac arrest.

After being stabilised and taken from the ground on a stretcher to applause from all four sides of Vicarage Road, the Hornets sought to continue where they had left off with their bold approach.

However, it was the visitors who struck first when poor defending allowed Mount to be set up for a straightforward opener.

Undeterred though, the Hornets deservedly got back on terms shortly before the interval when Moussa Sissoko won the ball back in midfield, immediately countered and set up Dennis to score his sixth of the season to make it 1-1 at the break.

Watford were unable to operate with the same sustained level of intensity after the interval, but they were looking largely comfortable until the 72nd minute when substitute Ziyech swept a low Mount cross beyond Bachmann to give the Blues the upper hand again.

Although the Hornets went into the game without longer term absentees Ben Foster, Ismaila Sarr and Nicolas Nkoulou, the injury situation was not as bad as feared building up to the match.

Dennis and Adam Masina were both fit to play despite being pre-game doubts, meaning Claudio Ranieri made just the one change from the team that lost 4-2 at Leicester City, with Joao Pedro replacing Cucho Hernandez.

Chelsea came into the game defending an 11-game unbeaten run in all competitions and Thomas Tuchel decided to shuffle his table-topping pack, making six changes from the side that was held to a 1-1 draw by Manchester United.

In came Andreas Christensen, Cesar Azpilicueta, Saul, Christian Pulisic, Mount and Kai Havertz. Jorginho and Timo Werner, who were pre-match doubts, were among the substitutes, but Reece James was not involved.

The Hornets, who started with Dennis on the right and Joshua King leading the offensive line, attacked the Rookery in the first half like they did against United and, as in that 4-1 victory, sought to press Chelsea from the outset.

Tom Cleverley was again leading by example in this regard and in the third minute he got away down the right and pulled the ball back for Pedro, who didn’t connect cleanly with a first-time right-footed effort on the half turn but it still had to be cleared with Edouard Mendy stuck to his line.

An injury caused play to cease for a minute but when it restarted Cleverley whipped in a dangerous cross from the right which Pedro got a glancing header on, the ball deflecting off Azpilicueta and forcing Mendy to dive to his right to save.

The Chelsea keeper was then almost caught in possession by King as the Hornets’ very encouraging start to proceedings continued, only for it to be halted when Masina signalled that he was unable to continue after hitting a deep left-footed cross.

Within seconds though, it was clear there was a much serious situation in the Graham Taylor Stand as stewards, medical staff from both teams and in the ground rushed across to help a fan who had been taken ill after other supporters had urgently called for help.

Fans were then notified off the medical emergency over the tannoy and referee David Coote rightly made the decision to temporarily suspend the game.

The players were off the pitch for fully 25 minutes while the patient was treated before they left on a stretcher to applause from all sides of the ground after Amazon confirmed their condition had been stabilised.

As the players reappeared from the tunnel for a five-minute warm-up, it was confirmed the person had suffered a cardiac arrest and was being to neighbouring Watford General Hospital after their condition had been stabilised.

After Danny Rose replaced Masina, play restarted in the 12th minute with a clearance from Mendy – and it wasn’t long before the Hornets were pressing again.

Saul picked up the game’s first yellow card four minutes later for hauling down Dennis around 25 yards out to the right of centre, but Imran Louza could only hit the free-kick into the wall.

Chelsea had struggled to build an attack worthy of mention in the opening 20 minutes but that changed when Mount was able to get in behind the Hornets defence on the right side of the area and rifled in a shot which rebounded out off the near post.

Watford continued to look the better side but in the 29th minute they were unpicked with ease as Chelsea struck.

The home side failed to pick up Marcos Alonso as he latched onto a clipped pass forward down the left-hand channel from Antonio Rudiger and the Spaniard squared for Kai Havertz who in turn teed up Mount to pick his spot past Daniel Bachmann to make it 1-0.

Having got their noses in front, the European champions thought they had doubled their lead inside two minutes when a lapse in midfield allowed Mount to slip in Havertz who beat Bachmann, but the offside flag was immediately raised.

It was Mendy who was the next keeper called into action, dealing with a powerfully hit cross-shot from Rose after the ball had been played in from the right.

Watford had deserved something for their attacking efforts though, and two minutes before the break they got it.

Sissoko set the ball rolling by dispossessing Reuben Loftus-Cheek in midfield before bursting forward and sliding in Dennis who weighed up his options before hitting a low shot which deflected off Rudiger and into the far corner to make it 1-1.

The first half finished in a flurry of yellow cards as Louza, Alonso and William Troost-Ekong were all booked, the latter clearly winning the ball before forcefully clattering into Mount.

Before that though, Watford were in again when Dennis slipped in Sissoko on the right side of the area but his effort lacked sufficient power to beat Mendy.

Tuchel made a change at the start of the second half with Thiago Silva replacing Saul, meaning Trevoh Chalobah moved up into the defensive midfield role.

The Hornets had the first moment of attacking promise after the break when Cleverley slipped in King on the left side of the area, the striker squaring dangerously across the six-yard box where Rudiger cleared.

The start of the second half was punctuated by a number of free-kicks but the Hornets were almost in again when King held the ball up, fed Pedro and he immediately set Cleverley free with Mendy yards out of his goal, the keeper coming out on top as he blocked with his legs before taking a painful blow to his ankle.

While he received treatment, Chalobah also went down with an injury and he was unable to continue, his place being taken by Hakim Ziyech on the hour.

The substitute’s first meaningful involvement though, was to receive a booking for pulling back Pedro in the centre circle.

A run across the penalty from Havertz ended with a shot which Bachmann held at his near post, before Tuchel upped the ante even more by bringing on Romelu Lukaku for Azpilicueta.

Watford were looking comfortable but with 18 minutes remaining Chelsea again made their quality tell when Alonso found Mount in space behind Kiko Femenia and the England international centred for Ziyech to sweep a finish into the roof of the net and make it 2-1 after 72 minutes.

Juraj Kucka was already being readied to come on and he replaced Louza before play restarted.

Bachmann saved a Ziyech header from a Mount cross as the visitors sought to make the points safe, while Cleverley was booked for dissent before being replaced by Jeremy Ngakia with five minutes of normal time remaining.

Watford continued to press for an equaliser and six minutes of injury time afforded them additional time to try and get one.

A free-kick some 30 yards out looked on the optimistic side, but Kucka connected superbly with a piledriver that Mendy wasn’t taking any chances with as he pushed it over the top.

Bachmann went forward in a last throw of the dice when his side won a last-gasp corner, but Chelsea successfully repelled it to take home the points.

It was a night though, when the thoughts of all inside Vicarage Road remained with the fan who had been taken seriously ill in the first half.

Watford: Bachmann; Femenia, Troost-Ekong, Cathcart, Masina (Rose 12); Louza (Kucka 72); Dennis, Cleverley (Ngakia 85), Sissoko, Pedro; King. Subs not used: Elliot, Gosling, Fletcher, Tufan, Kabasele, Hernandez.

Chelsea: Mendy; Chalobah (Ziyech 60), Christensen, Rudiger; Azpilicueta (Lukaku 69), Loftus-Cheek, Saul (Silva 46), Alonso; Mount, Havertz, Pulisic. Subs not used: Arrizabalaga, Jorginho, Werner, Barkley, Hudson-Odoi, Sarr.

Bookings: Saul for a foul on Dennis (16); Louza for a foul on Alonso (45); Alonso for a foul on Dennis (45); Troost-Ekong for a foul on Mount (45); Ziyech for a foul on Pedro (65); Cleverley for dissent (84).

Attendance: 20,388.

Referee: David Coote.