Sebastien Haller's first goal in more than 10 hours of football provided a vital winner for West Ham as they won 1-0 at Southampton.
The French striker, recalled to the starting line-up for Felipe Anderson, turned Pablo Fornals' knock-down in off the far post in the only goal of the game in a much-improved Hammers performance, which relieves some of the considerable pressure on under-fire manager Manuel Pellegrini.
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The Chilean's position had been discussed by the West Ham hierarchy in the wake of their 3-1 defeat against Arsenal on Monday, but the manager and his board will have been delighted by the Hammers' resolve in a game where Southampton registered only two shots on target across 90 minutes.
Michail Antonio thought he had doubled the visitors' lead seven minutes after half-time but a handball in the build-up was spotted by a VAR review, before Southampton finally sprung into life during a final 20 minutes where Danny Ings twice struck the woodwork.
But even that could not inspire his side to a comeback win which would have lifted them out of the relegation zone and instead they stay 18th, while West Ham rise to 15th on the back of only their second win in 10 games.
How West Ham relieved pressure on Pellegrini
West Ham put their fragile confidence to one side to dominate the opening stages of the game at St Mary's, but had only a half-chance to show for it when Fornals' shot was blocked at close-range by Cedric.
They continued to have the better of the play and should have won a penalty 25 minutes in when Roman Bednarek somehow avoided punishment for grabbing Antonio in a headlock inside his own area, even after a video review by VAR official Jon Moss.
West Ham put that disappointment behind them to take the lead through a welcome source, as the recalled Haller ended a run of 636 minutes without a goal with a slightly scuffed effort which went in off the far post to leave Alex McCarthy helpess.
That prompted a change in personnel and shape from the hosts at the interval, with Oriol Romeu replacing Nathan Redmond as Ralph Hasenhuttl looked to build a more solid foundation to mount a second-half comeback.
But within 90 seconds his side were close to falling two behind when Bednarek's slip allowed Haller's left-wing cross to find Fornals, and his rising first-time effort was only kept out by a strong McCarthy save.
They thought they had been breached again when Antonio beat two challenges before burying the ball into the far corner, but had VAR to thank for another close shave when it was spotted the ball had struck the West Ham man's arm en route to goal.
Southampton named an unchanged team despite suffering defeat at Newcastle last weekend.
The only change from West Ham's 3-1 loss against Arsenal saw Sebastian Haller recalled for Felipe Anderson, who was ruled out with illness.
Southampton should have taken some solace from that let-off with the noise level among the home support raised several notches, but they took a while to build up any momentum from their reprieve.
That changed when out of nothing, 20 minutes from time, they found themselves inches away from an equaliser when Ings' spectacular turn and shot rattled the underside of the bar with David Martin beaten, and the in-form striker struck the woodwork again moments later before he was wrongly flagged offside.
He could feel hard done-by minutes later, when he did find the back of the net with a wonderful 25-yard curling effort but was denied a spectacular equaliser as Martin Atkinson had already blown for a soft foul on Andriy Yarmolenko.
Southampton: McCarthy (7), Cedric (7), Stephens (5), Bednarek (6), Bertrand (6), Djenepo (5), Hojbjerg (5), Ward-Prowse (6), Redmond (5), Ings (7), Long (5)
Subs: Romeu (6), Armstrong (n/a), Adams (n/a)
West Ham: Martin (6), Fredericks (6), Ogbonna (7), Balbuena (7), Cresswell (7), Rice (7), Noble (7), Antonio (8), Fornals (7), Snodgrass (6), Haller (7)
Subs: Yarmolenko (6), Sanchez (6), Diop (n/a)
Man of the match: Michail Antonio
West Ham still carried a threat on the break and forced Martin into a couple of routine saves as full time approached, but Southampton continued to improve and again should have levelled when an unmarked Pierre-Emile Hojbjerg fired wide from Cedric Soares' low cross.
James Ward-Prowse struck a late free-kick straight at Martin from 25 yards with Southampton's first shot on target since the 13th minute, and it would be there last. A serenade of boos met the final whistle from three sides of St Mary's as Southampton remained inside the bottom three, while Pellegrini looks to have given himself more time to turn things around - for now at least.
What next for Hasenhuttl?
Southampton's brief resurgence, with back-to-back home wins, was ended with the West Ham defeat but after full time, Sky Sports pundit Jamie Redknapp said he felt the Saints board still had faith in Hasenhuttl.
He said: "It there was a moment to act [the 9-0 defeat to Leicester] was certainly it because that's rock bottom for any manager.
"I look at the players with Southampton, he went almost with a 4-2-4 first half and I look at Redmond, he didn't produce anything in the game, he never really went to go by anyone, never did any moments of magic.
"[Moussa] Djenepo they spent big money on. Nothing. A couple of stepovers in the first half, second half he did slightly better I would say when they did the system change. Shane Long I always feel is a better player coming off the bench to make an impact.
"That Southampton side they've got to do more. I need to see more from the players going forward and sometimes you can't look at the manager for that the players have got to do it."
Noble: A defining moment in our season
West Ham midfielder Mark Noble spoke to Sky Sports after the game and said: "Tonight for us, I think was a defining moment in our season because it showed we can be under the cosh for the last five minutes and still defend really well.
"You need a bit of luck in the game and we got that tonight. We could have scored a couple more but all in all to come here and get a 1-0 win - they're a good side, they've not been in bad form lately - we're really pleased.
"That's why tonight was so important can you imagine going into [Christmas] with a loss? It would have been horrible. We've got a couple of days off now so I can speak to my kids tonight without having the hump!
"I'm half looking forward to driving home and having three hours on the coach just because we've won. It just changes everything.
"You could hear the crowd getting frustrated with them playing around the back and we knew that was going to happen because it happens at our place. When you keep playing and playing and the crowd just wants you to go forward, the pressure builds."
What the managers said...
Southampton boss Ralph Hasenhuttl: "It was a big chance to move out of the relegation zone, we didn't take it and that's why we're very frustrated today. They tried everything in the second half, we tried to put more pressure in them, and we have to do better against Aston Villa.
"It's a long journey until the end of the season and the league will not be decided in December or January. We will keep fighting until the end of the season. More important [than the club's backing] is whether we develop our game. We could have got the points today but we didn't."
West Ham manager Manuel Pellegrini: "First of all, we won a game again. It's three points more, that's always important to keep a clean sheet, and the players recovered the trust that they can do it. Against Arsenal we did 60 minutes, but you need to play for 95 minutes. This game was very similar to the game we played against Chelsea.
"We have 12 days until our next game, hopefully we can recover Manuel Lanzini and Lukasz Fabianski."
Man of the match - Michail Antonio
A goal would have rounded off another powerful performance from Michail Antonio, whose persistence helped create Haller's first-half winner and came close to grabbing them another moments later when he kept the ball alive on the byline.
Antonio made more key passes (three) than anyone else on the pitch and competed in the most duels (28) too.
- West Ham have won more Premier League games against Southampton than they have vs any other side (17), while only at Fulham (7) have they won more away games in the competition than against Saints (5).
- West Ham have won a league-high 63 per cent of their Premier League points this season in away games (12/19).
- West Ham's Pablo Fornals has provided three assists in his last four Premier League games - as many as he had in his previous 48 appearances in the top five European leagues.
- Southampton have conceded at least once in their last 14 Premier League home games, the longest run without a home clean sheet in the competition since Crystal Palace went 15 in May 2015.
Southampton's next game is a 3pm trip to Aston Villa next Saturday, while West Ham are not back in action until Boxing Day when they visit Crystal Palace at 3pm. Their game next weekend against Liverpool was postponed because of the Reds' involvement in the Club World Cup.