South Korea's Ji Dong-Won struck in injury time as Sunderland dramatically beat Premier League leaders Manchester City 1-0 at the Stadium of Light on Sunday.
The result left City locked on 45 points with Manchester United and ahead on goal difference alone after they failed to make the most of the champions' shock 3-2 defeat by relegation-threatened Blackburn at Old Trafford on Saturday.
It was another frustrating away day for City following their goalless draw against West Brom.
City manager Roberto Mancini was left bemoaning his luck following a match where the visitors had the majority of the chances.
"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.
"A team like us can't concede a goal on the counter-attack at the end.
"We missed a big opportunity today because we had a chance to go three points on Manchester United."
There were barely 10 seconds left of added on time when substitute Ji was played in by Stephane Sessegnon and beat England goalkeeper Joe Hart from close range, although replays suggested the match-winner was offside.
For Sunderland manager Martin O'Neill, the result -- which lifted the Black Cats to 13th place, six points clear of the relegation zone -- was a testament to his side resolve.
"It was a remarkable performance by the team," said O'Neill, appointed nearly a month ago after Sunderland sacked Steve Bruce.
"We had a lot of problems beforehand, problems during the course of the game and obviously problems with Manchester City.
"The spirit is fantastic. Two things (summed it up): Seb Larsson yesterday (Saturday) was in bed all day, couldn't stand up really, but he was determined to play the game. He saw the game through."
O'Neill also praised recalled goalkeeper Simon Mignolet, in for the ill Keiren Westwood, who played in a protective face mask after fracturing his nose and eye-socket in October.
"The goalkeeper has done four, five days' training since the injury.
"His performance was fantastic."
City substitute Micah Richards nearly won the match for the visitors with two minutes left when he saw a header come back off the crossbar.
In the first half, City striker Edin Dzeko was denied by Mignolet and the woodwork.
Dzeko's 32nd minute shot was blocked by the keeper and three minutes later the forward clipped the bar while Samir Nasri's effort was cleared off the line by Craig Gardner.
But Sunderland could have been ahead early on when striker Nicklas Bendtner was left one-on-one with Hart only for the keeper to come out on top.
And one of the best chances of the second half fell to the Black Cats when Sessegnon outpaced the City defence only to screw his shot wide with just Hart to beat.
In the day's other Premier League match, a substitute also proved the match-winner as Nigeria striker Victor Anichebe came off the bench to score three minutes from time in Everton's 1-0 win away to West Brom.
Victory for Everton saw them climb to ninth place in the table and dropped West Brom down into 12th spot.
"There were very few chances," said Everton manager David Moyes.
"We were quite brave, we put a couple of forwards on and it paid dividends."
Disappointed Baggies boss Roy Hodgson said: "I don't think we played very well to be honest.
"Everton didn't have to do too much to keep us out so 0-0 would have been a satisfactory result."