Jason Puncheon came off the bench to grab a point for Southampton and all but secure their safety, just as it looked as though Sunderland had saved themselves in their Barclays Premier League clash at the Stadium of Light.
The midfielder struck with 14 minutes remaining after fellow substitute James Ward-Prowse provided the ammunition to cancel out Phil Bardsley's opener, and in the process left the home side still looking over their shoulders.
A point will still prove enough if Wigan lose at Arsenal on Tuesday evening for Paolo Di Canio's men and only a heavy defeat on the final day coupled with other results going against them will see Mauricio Pochettino's side go down.
Puncheon's strike came as a hammer blow to the Black Cats, who looked to be on the road to a precious victory after Bardsley, only recalled to the starting line-up because of Craig Gardner's suspension, drilled a superb 68th-minute shot past Artur Boruc.
But the cheers among a crowd of 41,988 turned to groans within eight minutes as Puncheon prolonged the agony.
Both sides started the day still far from assured of their top-flight status, but knowing victory would end their fears of slipping into the npower Championship.
But the first-half unfolded as a largely turgid affair with the visitors playing much of the football, but lacking a cutting edge, and their hosts failing to summon up the passion for which Di Canio had called in advance of a key fixture.
The Italian was down to the bare bones in terms of selection with Gardner having joined Stephane Sessegnon on the suspended list and with both Lee Cattermole and Steven Fletcher injured the lack of depth in his squad was exposed by a bench boasting little or no Premier League experience.
Southampton, who kicked off one point and a single place head of the Black Cats, started confidently with Adam Lallana dictating from the middle of midfield, and it was they who created the better chances.
Skipper Rickie Lambert steered a shot harmlessly wide from Lallana's seventh-minute free-kick, but despite his side's early dominance, they struggled to create further openings in a tepid first 25 minutes or so.
However, as the half wore on, keepers Simon Mignolet and Artur Boruc had to pay greater attention as the game started to open up.
The Belgium international had to make a fine reaction save to keep out Jay Rodriguez's 32nd-minute snapshot and was then grateful to see Lambert scuff another effort wide of the far post four minutes later.
But he was even more relieved with three minutes of the half remaining when Lambert managed to control Steve Davis' driven cross, but failed to get any power into his shot, which the former Sint-Truiden man blocked with his foot.
In the meantime, Boruc had got down to claim Adam Johnson's weak shot after John O'Shea had headed down a Larsson corner, but Davis had to make a brave block on the stroke of half-time to keep out the Swede's drive.
Di Canio made his move at half-time when he sent striker Connor Wickham on for winger James McClean to popular acclaim, a move which saw Johnson return to a wide position after playing the opening 45 minutes as an auxiliary frontman.
Wickham's aggression immediately gave the home side greater presence, although it was the Saints who continued to make the better chances with central defender Jose Fonte powering in a 51st-minute header from a Davis corner which forced Mignolet into another good save.
However, Sunderland might have taken the lead within seconds when full-back Danny Rose, playing the final game of his loan spell from Tottenham - the Black Cats' opponents next weekend - fired the ball across the face of goal only for Danny Graham to completely miss his kick as the chance to claim a first goal in a red and white shirt passed him by.
Mignolet was in the right place at the right time to claim Rodriguez's header from another Davis corner with 58 minutes played with his defenders having let him down once again.
But it was the Black Cats who took the lead in superb style with 22 minutes remaining.
For once, the Saints found themselves pinned back inside their own penalty area and when Johnson slid to ball to the overlapping Bardsley, he smashed a right-foot shot across Boruc and with the help of a slight deflection off Jos Hooiveld, inside the far post to spark mass celebrations inside the Stadium of Light.
But the joy was short-lived after Pochettino made a double change which paid off within four minutes.Ward-Prowse crossed from the left for Puncheon to power a header towards goal, only to be denied by the brilliance of Mignolet, but the Saints man reacted first to poke the rebound into the roof of the net.
It could have been even worse for the home side had the Belgian not palmed away Lambert's 87th-minute effort on yet another day when he proved their most dependable performer.