Then five minutes later Ilkay Gundogan doubled City's lead.
Earlier this season, they had gone on a run of games where they had won, but conceded goals due to defensive lapses.
Kevin De Bruyne is everything that Paul Pogba should be and Jose Mourinho must resort to disciplining him if he wants to get the best out of the 25-year-old, says Steve McClaren.
Mourinho's pep talk sparked a comeback that defied belief.
Within 5 minutes and 15 seconds, the ball was in David de Gea's net again.
City took control and if that goal demonstrated their grit, the second reflected their guile. Kompany was signed a week before the Abu Dhabi takeover in 2008 and he has been an integral part of the team's transformation, battling through more than 40 injuries in his City career. Sterling, starting after being left out against Liverpool, was the main culprit, firing over twice when clear and then straight at De Gea.
Just before United's remarkable revival Gundogan also hit the woodwork. Big signings, big games and they proved to be big players.
For the first goal, Sanchez drew him out of position, creating space for Ander Herrera to cushion the ball to Pogba.
From being derided for failing to justify his £89 million fee, the Frenchman was deadly.
City were left justifiably aggrieved after Ashley Young flew in on Sergio Aguero in the penalty area, but no spot-kick was given.
"I think there's no better feeling than to score that victor in a derby and obviously make up for the first goal, which was my mistake", the defender said. It will give the United players confidence that they can beat City on their own patch ahead of next season, but it's not much more than that. I'm not interested which is the liar and which is the honest guy. "I know, he knows, everyone knows, he had some performances not at the level of expectations we have for Paul".
"I could tell you many reasons why we didn't win". Manchester City went into halftime up 2-0, and it could have easily been 4-0 or 5-0 if not for Raheem Sterling blowing his chances.
The immediate implication of the loss was the postponement of their title celebrations, which will surely still happen at some stage in the coming weeks with Pep Guardiola's side enjoying a 13-point lead. He said: "Our challenge is to finish second but I want to congratulate City for the title because they are going to win and deservedly. I hope they win against Tottenham".