Chris Smalling made up for his first-half clanger by scoring a dramatic victor after Jose Mourinho had urged his players at half-time not to become the Etihad clowns.
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It was probably his best game in a United shirt.
Then in the 69th minute, Chris Smalling redeemed himself - he was at fault for Kompany's opening goal - by volleying home from an Alexis Sanchez free-kick to send the visiting support into raptures. And City should have had a penalty when Ashley Young somehow escaped without punishment from a knee-high lunge on Aguero inside the area that sparked an bad-tempered finale.
City, needing to win to wrap up the English top-flight title with more games to spare than any other side in history, seemed to be coasting to the landmark, leading their neighbours 2-0 at the break with goals from Vincent Kompany and Ilkay Gundogan.
Meanwhile, the loss to their city rivals is only the second time this season that Man City have experienced defeat in the league, and they are still in the running for a treble this season.
The £89 million midfielder has come in for plenty of criticism this season, with Pep Guardiola's revelation that Manchester City were offered the Frenchman in January only serving to fan the flames.
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Englishman Tom Curran, Starc's replacement, is a handy all-rounder but he is yet to play in India and will be watched closely. That in Kohli's opinion is the biggest transformation they have already achieved, even before the first ball has been bowled.
"That's why I congratulate Man City because they are going to win the title, they deserve to win the title". "A top, top player".
"I told (Nemanja) Matic, (Ander) Herrera and Pogba that they could not improve a lot from what they did in the first half because they had confidence to play and to move the ball and give passes".
City were stunned - flaws exposed. He said that he didn't want us to be the clowns who stand there watching them win their trophy'.
"That in practical terms and finish next season to finish second third or fourth is exactly the same, you don't win the title but qualify for the Champions League group stage".
Their next game in the Premier League is away against top-four side Tottenham Hotspur.
The France worldwide, 25, was dropped for both legs of the recent Champions League last-16 tie against Sevilla, which fuelled talk of a falling-out with manager Jose Mourinho.
Paul Pogba, a mere bystander in the opening 45 minutes, came alive after the restart, bagging a 97-second brace to turn the game on its head, leaving City shell-shocked.