The optimism coming into Watford’s opening game of the season has been rapidly replaced by early concern after the Hornets crashed to a 3-0 defeat at home to Brighton & Hove Albion.

The first five minutes was promising, but this was soon to be replaced by the Hornets withdrawing into their shell and then descending into an increasingly dispiriting and disjointed display as they were a clear second best all over the pitch and finished well beaten.

The Seagulls capitalised on some sloppiness at the back midway through the first half when Abdoulaye Doucoure scored the first goal of the season, but in the wrong net as he turned a Pascal Gross pass past Ben Foster after new signing Craig Dawson had initially given the ball away

Andre Gray wasn’t far away from equalising eight minutes into the second half but, that chance apart, the home side were disappointing going forward and were to go 2-0 down when substitute Florin Andone netted with his first touch.

But worse was to follow as Lewis Dunk was allowed to meander forward and was not closed down and his pass put another substitute, Neal Maupay, in the clear to score on his debut.

Javi Gracia’s first team selection of the new season saw Dawson the only one of the four summer signings to be involved in the match-day 18.

Gray’s good pre-season scoring form was rewarded with a place up front alongside captain Troy Deeney, while Gerard Deulofeu was preferred to Roberto Pereyra on the left.

The Argentina international was on the bench alongside Heurelho Gomes, who was preferred to Daniel Bachmann as the back-up goalkeeper.

The Seagulls had been busier than their opponents in the summer window, but none of their new signings were included in the starting XI for Graham Potter’s first game in charge.

However, four of the new recruits – Maupay, Leandro Trossard, Adam Webster and Aaron Mooy – were on the bench if required.

The volume in Vicarage Road was cranked up before kick-off, first to welcome new signings Danny Welbeck and Ismaila Sarr and then, in a clearly very popular move with the fans, the return of Z Cars.

Attacking the Rookery in the first half, Watford were straight on the attack and won their first corner of the season after 30 seconds. However, Jose Holebas’ delivery from the right was disappointing as his cross failed to beat Dale Stephens at the near post.

Deulofeu tried a curler from the edge of the area, but got his effort wrong as the high intensity start continued. But it was the visitors who were to have the first on target attempt of the afternoon when Martin Montoya pulled a low cross from the right back for Jurgen Locadia, whose first-time effort was safely held by Foster.

The hosts responded in kind, with Mat Ryan behind Deeney’s right-footed strike from the right side of the 18-yard box, before Foster opted to let a Davy Propper strike from distance go, although it ended up being somewhat closer to the goal than the Hornets keeper probably expected.

Watford’s fast opening had given a way to a more even contest, with the home side content to let Potter’s side have the ball in areas where they could cause no harm.

The Hornets did though, cause a problem for themselves when Craig Cathcart’s sideways pass to Kiko Femenia was picked off by Solly March, who accelerated away. The Seagulls had men over as the ball was worked form left to right, but Glenn Murray’s cross-cum-shot drifted harmlessly wide.

It was a warning that was not heeded and in the 28th minute the Seagulls took the lead.

After Dawson had initially given the ball away, some more sloppy defending saw Holebas fail to get enough distance on a header from a Stephens delivery, the ball fell for Gross on the right side of the area and his cut back was turned past Foster by Doucoure.

The home side tried to respond immediately, with Will Hughes dragging a shot on the turn wide. But there were alarm bells ringing in the Brighton defence in the 35th minute when Holebas knocked a free-kick sideways to Etienne Capoue, he drove the ball forward to Femenia who had got free on the right side of the area and turned the ball into the danger zone where some frantic defending saw it put behind for a corner.

Ryan was forced to tip behind a Holebas inswinging free-kick from distance that was helped on its was by the strong wind as the Hornets tried to get back on the terms before the break, but the half-time whistle blew with Gracia having plenty of work to do after a largely poor opening 45 minutes.

The Hornets head coach wasted no time in changing things, bringing on Pereyra following an ineffective first half on the left from Deulofeu.

The second period started with the floodlights being turned on before a brief downpour, but it was the visitors who continued to look the sharper in the opening stages.

However, Watford were almost back on terms eight minutes after the restart when Femenia robbed Dan Burns on the left side of the penalty area and pulled the ball back for Gray, who struck firmly towards the target only for his effort to be repelled by Dunk’s outstretched leg.

The first VAR check at Vicarage Road took place just shy of the hour mark when a Pereyra free-kick struck the end of the Seagulls wall.

The former Juventus man appeared adamant he had a good case for a penalty and let referee Craig Pawson know it, bit a decision in the Hornets’ favour was not forthcoming after the replays had been checked.

Potter made a double change in the 63rd minute, bringing on Andone and new signing Maupay for Locadia and Murray. It was to reap instant rewards.

This time Holebas didn’t take the opportunity to clear on the right and Propper capitalised, playing in a low cross which Andone swept home at the near post to score with his first touch to make it 2-0.

It was looking a long way back for the Hornets, but they did create an opportunity with their next attack when Femenia’s deep cross from the right was headed down by Dawson at the far post but Ryan was able to gather comfortably.

Isaac Success replaced Gray with 15 minutes remaining but it was soon to get even worse for the hosts.

Dunk picked up the ball in defence, jogged forward and with nobody attempting to shut him down he carried on and, spotting the run of Maupay, he picked out the substitute with one pass. And the former Brentford man calmly did the rest, rounding Foster to make it 3-0.

Watford were beaten and the increasingly large numbers of Hornets fans heading for the exits before the end reflected this.

Dawson wasn’t far away from scoring a consolation in the last minute when he was goal-bound strike was cleared off the line after Pereyra had headed the ball down into his path.

But the final whistle was to sound to a brief chorus off boos as the Hornets suffered a big wake-up call as they suffered defeat in their first game of a campaign in 13 years.

Watford: Foster; Femenia, Dawson, Cathcart, Holebas; Hughes, Doucoure, Capoue, Deulofeu (Pereyra 46); Gray (Success 75), Deeney. Subs not used: Gomes, Janmaat, Cleverley, Sema, Kabasele.

Brighton & Hove Albion: Ryan; Duffy, Dunk, Burn; Montoya, Propper, Stephens, March (Bernardo 90); Gross, Locadia (Andone 63); Murray (Maupay 63). Subs not used: Button, Trossard, Webster, Mooy.

Bookings: Dunk for a foul on Hughes (88).

Attendance: 20,245.

Referee: Craig Pawson.