(CNN) -- South Korea's Ji Dong-Won grabbed a dramatic injury-time winner as Sunderland stunned English Premier League leaders Manchester City 1-0 at the Stadium of Light Sunday.
The upset result left City ahead of champions Manchester United on goal difference, having gone into the match hoping to open up a three-point lead after their neighbors were beaten 3-2 by Blackburn 24 hours earlier.
Instead, Roberto Mancini's men were left to reflect on a wasted opportunity with cavalier defending in the dying moments costing them even a point.
Sunderland, who had been penned in their area for much of the final few minutes, broke upfield and had a two-man advantage as Stephane Sessegnon played in Ji.
On as a substitute for Niklas Bendtner, he beat England goalkeeper Joe Hart with a composed finish.
Moments before City substitute Micah Richards had thumped the crossbar after Simon Mignolet parried a David Silva shot.
Edin Dzeko hit the woodwork in the first half as the leaders dominated possession, but the home side also had clear-cut chances.
Bendtner wasted his before the break and Sessegnon screwed his effort wide in the second half.
The three points lifted Sunderland, who have been revived under new manager Martin O'Neill, to 13th place, six points clear of the drop zone.
City must now entertain Liverpool on Tuesday night as they look to get their title challenge back on firmer footing.
Mancini bemoaned his side's luck after the surprise defeat.
"We deserved to win this game," he told Sky Sports. "It's incredible.
"This is football. I don't know how many chances we had," the Italian added.
"We missed a big opportunity today because we had a chance to go three points on Manchester United."
It completed a weekend of upsets with none of the top five, bar Arsenal, winning.
Tottenham stayed in third, six points behind the Manchester pair with a game in hand, after being held at Swansea.
In Sunday's other game, Nigerian international Victor Anichebe came off the bench to score the only goal of the game in Everton's 1-0 win away to West Bromwich Albion.