Southampton have all but confirmed their Premier League status for another season courtesy of a 1-0 win over Swansea City, who must now win their final game of the campaign to stand any chance of staying up.
Manolo Gabbiadini came off the bench to score the only goal of the contest at the Liberty Stadium as Southampton recorded a priceless victory which leaves them 16th in the Premier League table and three points clear of the relegation zone with just one game remaining.
The Saints are now guaranteed survival if they avoid defeat against champions Manchester City on the final day, while even a loss in that match will not be enough to send them down unless there is at least a 10-goal swing in goal difference.
Swansea, meanwhile, most hope that Huddersfield Town lose their final two games of the season - against Chelsea and Arsenal - and also that they beat the already-relegated Stoke City on the final day if they are to stay in the top flight.
Southampton's victory this evening also condemns West Bromwich Albion to relegation from the top flight, with only a draw in South Wales being enough to take the Baggies' remarkable escapology efforts to the final day.
Southampton were the first to have a shot on goal in what had been billed as essentially a winner-takes-all encounter, but Ryan Bertrand's long-range effort was tame and never seriously troubling Lukasz Fabianski in the Swansea goal.
There was more testing work for Alex McCarthy to do at the opposite end just a minute later when Andy King - one of three changes to Swansea's starting lineup - poked a snapshot towards goal which needed a smart save from the Southampton keeper.
It took a last-ditch challenge from Jan Bednarek to deny Andre Ayew a clear sight of goal after good work from Jordan Ayew, and referee Michael Oliver rejected Swansea's subsequent appeals for a penalty after the ball had rebounded against an unwitting Wesley Hoedt's arm.
Both sides struggled to get into any real rhythm during a scrappy and understandably edgy affair, but Swansea's tactic of testing Southampton with crosses into the box was clear and it almost provided the opener after 26 minutes when Ki Sung-yueng hoisted the ball back into the area for Jordan Ayew, who could not keep his difficult header down.
Charlie Austin's lack of involvement in the opening half-hour saw him snatch at a long-range effort when the ball broke to him in a promising position, but the Southampton striker had a better chance moments later as Fabianski was forced into his first meaningful save.
A through-ball from Pierre-Emile Hojbjerg sent Austin running through on goal for the first time, but his low drive towards the bottom far corner was too close to the Swansea keeper, who got down to make the save.
The home side's pressure did begin to grow in the final 10 minutes of the half, and the closest they came before the interval arrived when Sam Clucas met King's cross with a glancing header, sending the ball bouncing narrowly wide of the far post.
Southampton repelled cross after cross as Swansea's pressure continued to grow, but the visitors almost nicked a late opener just two minutes before half time when Oriol Romeu flicked Cedric Soares's cross on to Austin, who fired a sweetly-struck volley straight at Fabianski.
It was a first half sorely lacking in individual quality, but Jordan Ayew almost provided that in the opening stages of the second half when he cut inside before unleashing a dipping long-range drive which forced McCarthy into an equally spectacular fingertip save.
Austin then tested Fabianski with another powerful drive at the other end before Jack Stephens failed to make the most of finding space from a corner at the back post, nodding the ball into the back of Kyle Naughton and behind for another corner.
Southampton really should have broken the deadlock from the resulting set piece as Cedric kept it alive on the right flank before picking out Austin, but once again the striker steered his header straight at the Swansea keeper when unchallenged in the middle of the area.
Carlos Carvalhal was the first to turn to his bench with an attacking sub as Tammy Abraham came on, and the youngster looked eager to make an impact with a low drive which was easy for McCarthy to gather.
It was a Southampton switch which changed the game, though, as Mark Hughes brought on Gabbiadini after seeing Bednarek suffer a head injury at the hands of his own goalkeeper, and the Saints manager's attacking gamble paid off just four minutes after his introduction.
A deep corner was nodded back into the middle and then flicked on by Romeu to Austin, who was once again denied by Fabianski. However, this time the ball bounced back out into the area and Gabbiadini reacted quickest to tuck the rebound home.
Suddenly Swansea were left facing the prospect of even a win on the final day not being enough to keep them in the division, but their efforts to save themselves from that fate yielded little joy and it was Southampton who continued to look the most like scoring in the closing stages.
Austin once again failed to truly trouble Fabianski with a header 10 minutes from time before Gabbiadini turned provider with a pass into the path of Shane Long, who blasted his finish into the side-netting.
Swansea did create one final half-chance in the six minutes of stoppage time when Abraham skilfully brought the ball down on his chest, but he was off balance when trying his half-volley on the turn and duly sliced it over the crossbar.
With that went Swansea's last hopes of getting a draw which would have arguably left them as favourites to survive considering the contrasting final-day fixtures as Southampton - who had thrown away leads on three occasions from Hughes's six games at the helm before tonight - held on before greeting the final whistle with jubilant celebrations.
West Brom also suffered from the Premier League's joint lowest-scorers failing to find the back of the net for a fourth game in a row as the result confirmed their relegation from the top flight on the same day that caretaker boss Darren Moore was named Manager of the Month.
Carvalhal's side will now be sweating on the result of Huddersfield against Chelsea on Wednesday night, with defeat for the Terriers in that match leaving Swansea needing a win on the final day, and for Huddersfield to lose against Arsenal, to stay in the division.
However, should the Terriers avoid defeat in either of their final two games of the season then Swansea - now without a win in nine including four successive defeats without scoring - would require an unlikely shift in goal difference on the final day to survive.
SWANSEA (3-5-2): Fabianski; Naughton (Narsingh 75'), Fernandez, Mawson; Roberts, Ki, King (Carroll 82'), Clucas, Olsson (Abraham 62'); A Ayew, J Ayew
SOUTHAMPTON (3-4-3): McCarthy; Bednarek (Gabbiadini 68'), Stephens, Hoedt; Cedric, Hojbjerg, Romeu, Bertrand; Tadic (McQueen 83'), Austin, Redmond (Long 64')