Jose Holebas' late strike denied Southampton a first Premier League win of the season at St Mary's as Watford came from behind to earn a 1-1 draw on Saturday.
Manolo Gabbiadini made the breakthrough after 20 minutes, the Italian's first top-flight goal in front of his own fans since scoring against Newcastle United 13 months ago.
Southampton: McCarthy (6), Soares (6), Yoshida (6), Hoedt (6), Bertrand (6), Armstrong (6), Lemina (6), Hojbjerg (7), Redmond (7), Gabbiadini (8), Ings (6)
Subs: Ward-Prowse (6), Austin (7), Obafemi (6)
Watford: Foster (7), Holebas (7), Cathcart (6), Mariappa (6), Femenia (7), Chalobah (7), Hughes (6), Doucoure (6), Deulofeu (6), Success (6), Pereyra (6)
Subs: Deeney (8), Gray (6)
Man of the match: Manolo Gabbiadini
However, after Charlie Austin had a goal controversially disallowed for offside midway through the second half, the visitors claimed a share of the spoils thanks to Holebas' deflected effort eight minutes from time.
As a result, Mark Hughes' side remain 17th in the table having won just once at home in the league this year, while Watford move up to seventh.
The Saints may have come into this game on a seven-match winless run, but after Gerard Deulofeu failed to beat Alex McCarthy when through on goal with an early chance, the hosts took control.
Ben Foster had to be alert to keep out Wesley Hoedt's initial close-range header, but the visitors were not so lucky from Nathan Redmond's next corner.
What would VAR have changed?
There is no doubt that had VAR been in operation at St Mary’s, then not only would Watford have been awarded a 58th-minute penalty after Ryan Bertrand impeded Nathaniel Chalobah in the box. However, the Video Ref would also have noticed that Charlie Austin’s strike did not take a deflection off Maya Yoshida on its way into the net midway through the second half.
The full back's delivery from the left was actually poor, allowing Roberto Pereyra the chance to clear his lines. However, the forward was caught in possession in the area by the alert Danny Ings, before the recalled Gabbiadini nipped in to fire his side ahead.
Javi Gracia's team thought they should have had a penalty just before the hour-mark when Nathaniel Chalobah - making his first start in over a year - was hacked down in the box by the already-booked Ryan Bertrand, only for referee Simon Hooper to deem it a fair challenge.
There was more controversy after 66 minutes following a fine run by Redmond, who found Austin just inside the area, with the substitute then beating Foster with the help of a slight deflection off a Watford player.
However, after consulting assistant Harry Lennard, Mr Hooper - in only his fourth Premier League game - decided incorrectly that it was Southampton defender Maya Yoshida, standing in an offside position, who had diverted Austin's shot past Foster and so was interfering with play.
Southampton made three changes from the side that lost 6-1 at champions Man City last time out, with Jack Stephens, James Ward-Prowse and Shane Long being replaced by Maya Yoshida, Stuart Armstrong and Manolo Gabbiadini.
Meanwhile, Etienne Capoue missed out due to suspension, with Nathaniel Chalobah replacing him in midfield in the visitors' only change from last weekend's 1-0 loss at Newcastle.
And that decision became even more unpopular with the Saints faithful when Watford levelled matters late on after James Ward-Prowse made a hash of a clearance, allowing Holebas to beat McCarthy with the help of a wicked deflection off Cedric Soares.
- Southampton have lost just one of their last 11 matches against Watford in all competitions (W5 D5)
- Southampton have failed to win any of their first six at home in a single league season in the top four tiers of English football for the first time
- Watford have failed to keep a clean sheet in 11 of their last 12 Premier League away games
- Watford's Jose Holebas has been directly involved in more Premier League goals this season than any other defender (2 goals, 4 assists)
- Southampton's opening goal was their first in the Premier League that wasn't from the penalty spot in 615 minutes since Pierre-Emile Hojbjerg netted vs Brighton in September
Mark Hughes: "Unfortunately the officials have cost us dearly today. At 1-0 to the good we get an opportunity, it is a clear goal, Charlie dispatches a chance in their box.
"A clear goal and not one of their players appealed for offside, we are celebrating it is 2-0 and the game is over in my view.
"Then all of a sudden the officials deem fit to play a hand for some reason, imagination or whatever, I have no idea."
Javi Gracia: "I didn't see it from my position, it's impossible to know what happened. But after asking Chalobah he told me it was clear and maybe changed the game from that moment. But I prefer to support the referee's decision, it's difficult their job."
Pundit - Phil Thompson
"This was astonishing (Austin's disallowed goal). This is not right. Everybody goes celebrating and there's not one of the Watford players who think there's anything untoward.
"The ball gets pulled back towards the edge of the box, Charlie Austin strikes the ball and it takes a bit of a deflection.
"You have Yoshida, who was standing what you consider at the far post or just outside and he makes absolutely no attempt to go anywhere near the ball.
"The ball is probably about a yard away from him and if anything, he just watches the ball sail past him into the back of the net. It's a goal.
"Simon Hooper gets this totally wrong - or he's taken information from his assistant on the side and who is further away. Looking at his angle, he might think he's interfering with the goalkeeper's line of vision.
"He's not. He's to the side of Ben Foster so he's not impeding his view. If he is being given information, he should overrule him because he can see Yoshida is not making any attempt to play the ball or impeding.
"It's a perfectly good goal. It's an easy decision that he (the referee) shouldn't get wrong."
Man of the Match - Manolo Gabbiadini
It has been a long time coming for the striker, but on Saturday he finally managed to find the net in the Premier League at St Mary's, 391 days after he last managed to do so against Newcastle.
That poacher's strike after 20 minutes appeared to give the Italy international - recalled in place of Shane Long - a much-needed boost in confidence.
And as a result, he was his side's best player on the south coast as he constantly stretched the Watford defence all afternoon long, while also looking a constant threat in front of goal.
Southampton take on fellow strugglers Fulham at Craven Cottage after the international break on Saturday, November 24.
Meanwhile, Watford face high-flying Liverpool at Vicarage Road on the same day.