SUNDERLAND'S survival bid received a massive boost as they became the first side to beat a Chelsea team managed by Jose Mourinho at Stamford Bridge.
Trailing to an early volley from Samuel Eto'o, Sunderland equalised when Connor Wickham stabbed home from close range before the interval.
While Chelsea dominated possession for the majority of the night, Gustavo Poyet's side defended superbly throughout, and they got their reward with eight minutes left.
Cesar Azpilicueta fouled Jozy Altidore in the area – although it was a marginal decision from referee Mike Dean – and Fabio Borini stepped up to convert from the spot.
The goal has major ramifications in terms of Sunderland's battle against the drop – and might well also see Borini's parent club, Liverpool, claim the title.
The Black Cats stay bottom, but they have moved to within three points of 17th-placed Norwich City ahead of next weekend's utterly crucial home game with Cardiff City.
Having watched his side claim a surprise point at Manchester City on Wednesday night, Poyet named an unchanged starting line-up for the only second time in his Sunderland career.
Unfortunately, the make up of the team wasn't the only thing similar to events at the Etihad Stadium, as for the second time in four days, the Black Cats gave themselves a mountain to climb with the concession of an early goal.
It was the 12th minute rather than the second this time around, the effect was the same, with Sunderland trailing to a title contender.
Set-pieces have been a major Achilles heel for the Wearsiders this term, and when Willian swung over a corner from the left, Eto'o held off the attentions of Lee Cattermole to hook the ball home with a first-time volley.
Vito Mannone might have been more decisive; Cattermole might not have made the bizarre decision to attempt an ill-advised stooping header. As it was, Sunderland once again found themselves a goal behind.
To their credit though, and just as they had at the Etihad, they produced a spirited response to their early setback.
On Wednesday, it had taken more than a hour to regain parity. At Stamford Bridge, it took just six minutes.
Seb Larsson spotted Marcos Alonso in acres of space as he lined up a corner, and his floated pass found the Spaniard perfectly.
Mark Schwarzer, playing in place of Petr Cech, could only parry Alonso's 25-yard shot, and Wickham reacted quicker than John Terry to stab home the rebound. Having gone more than a year without a Premier League goal, Wickham suddenly had three in the space of four days.
Sunderland went close to claiming the lead when Adam Johnson cut in from the flank and curled wide, but the rest of the first half was a one-way assault on the Sunderland goalmouth.
The Black Cats held firm, largely thanks to four excellent saves from Mannone, who successfully put the heartbreak of Wednesday's calamitous late concession behind him.
The Italian didn't know much about the first one, with Branislav Ivanovic's header cannoning off him before rebounding to safety off the crossbar.
The next two were much more impressive though, with Mannone parrying Nemanja Matic's low shot before scrambling to his feet to keep out Mohamed Salah's rebound.
Sunderland survived a penalty scare when Borini's header hit Alonso's arm in the box – it would have been a harsh decision given how close the two Sunderland players were standing to each other – and Mannone was called into action one minute before the break, blocking Willian's near-post strike after the Brazilian met Salah's low cross.
That wasn't the end of the first-half action, however, as Ramires thrust a trailing arm into Larsson's face as the interval approached. Referee Mike Dean clearly spot the incident, which should have resulted in a straight red card for the Chelsea midfielder.
The FA will almost certainly punish Ramires retrospectively, but that won't be much use to Sunderland, who should have been playing the entire second half against ten men.
As it was, 11-man Chelsea created the opening opportunity of the second period within three minutes of the restart, but Eto'o dragged a first-time shot wide after Willian's break had opened up the Black Cats' defence.
The hosts continued to dominate possession during the second half, but with Cattermole dropping deep to help support the impressive Wes Brown and John O'Shea, Sunderland's defence held firm with only sporadic scares.
Midway through the second period, Poyet introduced Emanuele Giaccherini and Altidore for Johnson and Wickham, while Demba Ba and Andre Schurrle came into the fray for Chelsea.
Fernando Torres came on with 16 minutes left as Jose Mourinho tried a final roll of the dice, and the Spaniard immediately fired the ball over the crossbar with an extravagant overhead kick.
Sunderland must have feared a late Chelse onslaught at that stage, but remarkably, it was the visitors that claimed the lead with eight minutes left.
Azpilicueta slipped to let in Altidore, and as he attempted to make up for his error, the Chelsea full-back lunged in to bring his opponent down.
Mike Dean pointed to the spot, and Borini calmly rolled the ball past Schwarzer. As a Liverpool loanee, the Italian almost certainly handed his parent club the title.
CHELSEA (4-2-3-1): Schwarzer; Ivanovic, Cahill, Terry, Azpilicueta; Ramires, Matic; Willian, Oscar (Ba 59), Salah (Schurrle 66); Eto'o (Torres 74).
Subs (not used): Hilario (gk), Luiz, Mikel, Lampard.
SUNDERLAND (4-1-4-1): Mannone; Vergini, Brown, O'Shea, Alonso; Cattermole; Johnson (Giaccherini 65), Larsson (Celustka 90), Colback, Borini; Wickham (Altidore 66).
Subs (not used): Ustari (gk), Ba, Mavrias, Scocco.