Southampton slipped to a third successive defeat as Watford gave their Premier League survival hopes a shot in the arm with a surprise victory at St Mary’s.
The visitors took a 2-0 lead in the first half thanks to a brace from Cucho Hernández, whose first goal was gifted to him by an under-hit back-pass, before he was afforded too much space in the box to double his tally.
Mohamed Elyounoussi pulled one back on the stroke of half time, prompting hopes of a revival, but Saints struggled to create chances all afternoon in a game lacking rhythm that played into the visitors’ hands.
James Ward-Prowse went close from a late free-kick, before substitute Armando Broja was denied by a flying save from Ben Foster, but Watford held on to boost their chances of a great escape.
Ralph Hasenhüttl made two alterations to his side following Thursday’s defeat to Newcastle at St Mary’s – just the second time Saints had been beaten on home soil all season.
The changes meant a tweak in system, as Will Smallbone replaced Broja, occupying a No. 10 role as Saints adopted more of a 4-2-3-1 shape.
Elsewhere, Tino Livramento was sidelined by a fitness issue, prompting Romain Perraud to take his place with Kyle Walker-Peters shifting to right-back.
Saints were sharp out of the blocks, creating the first chance of the game inside two minutes.
Walker-Peters fed Stuart Armstrong in front of him, whose cross from the byline was attacked well by Elyounoussi at the far post. His header was on target, back across the stranded Foster, but Brazilian defender Samir intervened with a vital clearance.
Saints dominated the opening 10 minutes, but Watford sprung to life and might well have had the lead when the ball dropped kindly for João Pedro in the box, who had time to take a touch and get his shot off, but Jan Bednarek was in the way, making a block equally as important as Samir’s at the other end to preserve parity.
The chance seemed to give the visitors some belief, and in the 14th minute the travelling fans could not believe their luck when Saints shot themselves in the foot to gift the opening goal to Hernández.
There seemed no danger when Bednarek played the ball back to Fraser Forster, but the keeper’s return pass was nearly intercepted by the lurking Hernández.
No matter, the ball was still in safe possession, but when Bednarek found Salisu to his left, the sloppiness became contagious, and the ensuing back-pass to Forster was short, allowing Hernández to get his rewards for his persistence by rounding the keeper to score.
When Ché Adams played a square pass out of play soon after, it was clear Saints had been affected by the goal and that sharp start suddenly felt a distant memory.
There were still moments of encouragement; Elyounoussi’s touch just got away from him in the box, while Walker-Peters burst into the box and hit the side-netting before Salisu headed a Ward-Prowse free-kick over the bar.
But Ben Foster was still yet to be tested in the Watford goal by the time the visitors scored their second on 34 minutes.
Emmanuel Dennis kept the ball in play on the byline and laid it back for Juraj Kucka to cross first time to the far post, where Hernández was left in too much space to volley home his second of the afternoon.
Saints did respond with a rasping drive from Walker-Peters beaten away by Foster at his near post, but St Mary’s was in a state of shock.
Things might have got even worse when Moussa Sissoko slipped the ball in behind the defence for Kucka to go one on one with Forster, but his touch was heavy and the keeper was out quickly to shut down the angles.
Saints were in need of inspiration and it finally arrived from a Ward-Prowse free-kick in the final minute of the first half.
The skipper’s delivery was helped on by Adams at the near post and in by Elyounoussi at the far, as he poached a goal back with a low finish back across Foster from six yards to halve the deficit just before the break.
Hasenhüttl’s response to a first half not to his liking was to introduce Broja for Smallbone, giving Adams a more orthodox strike partner and Saints an extra attacking threat.
The second period began with some tension in the air. Watford players were not in shy in going down to receive treatment, stifling the flow of things, while Perraud was booked for a cynical challenge and Walker-Peters was wiped out by Imrân Louza only for referee Graham Scott to play on.
By the hour mark Oriol Romeu was playing as a third centre-back, allowing Walker-Peters and Perraud to play much higher, with Ward-Prowse at the base of a midfield triangle behind Armstrong and Elyounoussi.
The game remained very stop-start, increasing the importance of set-pieces when they came.
Ward-Prowse had already had a hand in Elyounoussi’s goal when he sent in another teasing delivery, this time headed off target by Salisu, but Saints needed to carry a greater threat from open play.
Instead it was Watford posing problems when Kucka was afforded too much time on the edge of the box to set his sights on the top corner, sending Forster flying to his left to repel his shot as the clock ticked down into the final 20 minutes.
Saints reverted to a back four when Nathan Redmond was introduced in the 74th minute, which straight away left them exposed on the counter-attack when Hernández spurned the chance to complete his hat-trick by blazing over from 20 yards.
A desperate lunge from Bednarek on Dennis resulted in a yellow card for the Pole and a drinks break while the Watford man received treatment, as Hasenhüttl tried to relay his final instructions to his team, who were still struggling to carve out chances.
With four minutes to go Adams bought a foul on the edge of the box, inviting Ward-Prowse to step up, but the free-kick was so close to the area that he could not quite dip it in time to beat the rooted Foster, who has often been a victim of his dead-ball brilliance in the past.
The veteran stopper was flying to his left to repel Broja’s header from Redmond’s cross soon after, while VAR checked a late handball in the Watford box as Saints kept pushing for an equaliser, but again the visitors survived and Hasenhüttl’s men just came up short.