City miss a great chance after Mancini's rotation

Sunderland 1 Manchester City 0: South Korean comes off bench to stun Premier League leaders on weekend of major upsets

Ji whizz indeed. Less than 24 hours after Blackburn Rovers pooped Sir Alex Ferguson's birthday party at Old Trafford, Ji Dong-won lobbed a counter spanner into the works of the two-horse Mancunian Premier League title race. The 6st 2in South Korean striker did so in stunning fashion, conjuring a 93rd-minute winner that had the Sunderland manager, Martin O'Neill, threatening to launch into orbit from pitchside – and that no doubt brought a measure of belated new year cheer to the Ferguson household.

It left Roberto Mancini crestfallen and his team locked on 45 points with United, only goal difference still separating the neighbours at the halfway stage of the season. For City and their Italian manager, it was a missed opportunity to put some daylight between themselves and United.

A draw would have been a disappointment against a Sunderland side featuring a makeshift defence but Mancini's men were denied even that consolation when the home team broke from the back in the final minute of injury time and Stéphane Sessègnon squared a pass to Ji, a 78th-minute substitute for Nicklas Bendtner, and the 20-year-old – signed in the summer by O'Neill's predecessor, Steve Bruce, from Chunnam Dragons – dragged the ball wide of Joe Hart before squeezing home a left-footed finish.

The dejected Mancini disappeared down the tunnel without waiting for the final whistle. Having rested Mario Balotelli and several other big hitters, there were no goalscoring fireworks by his team for a second successive match. For a fourth League match in a row on the road, there were dropped points.

With tomorrow's visit of Liverpool in mind, Mancini rotated his squad at a little more than half-turn, making six changes to the starting XI from the goalless draw at West Bromwich Albion on Boxing Day. In came Joleon Lescott, Gareth Barry, Nigel de Jong, Adam Johnson, Aleksandr Kolorov and Edin Dzeko.

At least the City manager was fitting round pegs into spherical holes. Phil Bardsley and Titus Bramble having failed to survive the knocks they took in Sunderland's 1-1 home draw against Everton on Boxing Day, O'Neill was obliged to field central midfielders as full-backs – Craig Gardner on the right, Jack Colback on the left.

With Kieren Westwood also on the injured list and the Belgian Simon Mignolet stepping into the breach in the home goal, City's half-strength line-up did not lack encouragement. De Jong, Barry and Yaya Touré formed a fluid central midfield trio and they took an instant grip on proceedings. The younger Touré brother made serious inroads with a surging run before having a low drive deflected wide.

After breaking quickly from the blocked corner, though, Sunderland ought to have snatched the lead. Sessègnon's ball from just inside the home half put Bendtner in the clear but the Dane made a mess of the clear chance, taking a touch too many as Hart advanced and comfortably smothered his over-delayed shot.

It was a big let-off for City and while Hart also snaffled a long-range effort from James McClean, a hyperactive Irish left winger making his first Premier League start for Sunderland, the prevailing traffic was mainly one way. Much of it was up the right, the silken Touré linking with Johnson to good effect and giving the out-of-position Colback an uncomfortably hard time.

Sunderland-born and a Sunderland fan in his youth growing up in the Billy Elliot East Durham pit village of Easington, Johnson looked suitably at home and was not far off the bullseye with one of his trademark whizzbangs, cutting in from the right and unloading a left-foot shot that ripped narrowly over the bar. The former Middlesbrough winger also played a return pass to Touré that might have yielded the opener had the Ivorian not stumbled off balance as he shaped to shoot.

It was to Sunderland's credit that they managed to keep the visitors in harness as the opening half progressed – despite losing another defender, Wes Brown limping off, to be replaced by Matthew Kilgallon. Still, after the half-hour mark passed, City regained attacking momentum and there were a series of close calls for the home side.

Johnson drilled a ball into the goalmouth from the right and Dzeko hada first-time shot blocked at point-blank range by Mignolet. Samir Nasri had a low angled drive cleared off the line by Gardner. Then, from a partially cleared left-wing corner, Dzeko unleashed a left-foot drive from outside the area that smacked off the top of Mignolet's bar.

The Sunderland players received a standing ovation for reaching the interval on level terms. There were groans when the fourth official indicated that City would be sending out Sergio Aguero in place of De Jong for the second half but the visitors struggled to get into a groove after the resumption.

Any time the ball was shipped in Johnson's direction he was double-marked, McClean pushing back tosupport Colback. Such was City's frustration, Mancini did not wait long to throw on another member of his cavalry, David Silva replacing Nasri in the 54th minute. It almost paid dividends four minutes later.

Play was allowed to continue when Pablo Zabaleta bundled over Sessègnon, and Silva, Dzeko and Aguero were all involved in a slick attack through the middle that ended with the latter having a close-range shot saved by Mignolet.

At the other end, Sessègnon dragged a shot across the face of Hart's goal but City laid siege to the Sunderland penalty area for the final quarter of an hour and, with a minute of regulation time remaining, Mignolet parried a stinging drive and Micah Richards, City's third substitute, directed a header down and on to the bar.

If that was a stab to the solar plexus for Mancini, worse was still to come.