Chris Smalling made up for his first-half clanger by scoring a dramatic winner after Jose Mourinho had urged his players at half-time not to become the Etihad clowns.
Smalling knew he had messed up when allowing Vincent Kompany to outmuscle him for the City opener and the runaway Premier League led 2-0 at half-time.
But the England defender, who made amends with a brilliant strike after Paul Pogba’s quickfire double, said: ‘I owed them that.
‘When you make a mistake you want an opportunity to make amends. You could see the relief after the first goal and I’m just glad to contribute.’
United’s stunning turnaround wrecked City’s title celebrations.
Smalling continued: ‘We came in at half-time feeling sorry for ourselves and we knew that we needed to play with pride in the second half. The first half was terrible — dropped off, didn’t play our game and could have been out of sight.
‘The manager didn’t have to say much because we knew we’d let ourselves down. He said that he didn’t want us to be the clowns who stand there watching them win their trophy.’
#MUTV caught up with @AnderHerrera after the Spaniard's battling midfield performance in today's win.
(Plus, a surprise appearance from Nemanja Matic, who couldn't resist a selfie 👀) #MUFC pic.twitter.com/QHBCG1imoH
Pep Guardiola was disappointed at losing and clearly concerned at having conceded six goals in four days after their 3-0 hiding at Liverpool in the Champions League.
The City boss said: ‘We have to defend better but that’s football. Our team tried to create and attack, that is what we have done all season, we tried to produce all of that quality and goals.
‘You have to defend a little better in the second half, but it is football. But as far as our intention, there are no complaints.’
Guardiola continued: ‘A special day for United which is a pity. They found their game, they have their spirit.
‘We did absolutely everything in the first half but then for 10 to 15 minutes we conceded goals. It is what it is.
‘We played with courage and created so many chances in the first half. But we have to improve. We were not good enough in the end.’
United’s win cut City’s lead at the top to 13 points with six games left and Mourinho was happy to congratulate his opposite number on the final whistle.
He said: ‘I got the chance to congratulate City. They are frustrated because they wanted to do it today but I congratulated them because they will win it and they deserve it.
‘They’ve got more points than others and have more wins than the others.’