United's late win was something few – perhaps not even Amorim himself – saw coming as a game that had been so undistinguished appeared to be moving towards an uneventful conclusion.
And then, in a final few minutes totally out of keeping with the mediocre fare that had gone before, United gave Amorim a personal triumph that will instantly increase his standing among United's supporters.
United had barely been troubled by Pep Guardiola's off-colour Premier League champions, but had created little of the their own, that Fernandes chance apart, until the always lively Diallo took a hand.
He collected a poor pass from Nunes in the 88th minute, who then compounded his error by chasing back and flattening the United forward with a reckless challenge, allowing Fernandes to make up for his earlier miss.
Diallo then showed real composure in the final minute of normal time to squeeze in United's winner from a title angle, Etihad Stadium stunned into silence apart from the ecstatic visiting fans.
Amorim took two big decisions to ditch Rashford and Garnacho from his squad completely, an early indicator that he will not shy away from difficult calls, no matter how big the profile of the player involved.
It had the desired impact, albeit late on, as United returned to winning ways in the most satisfying way possible after losing at Arsenal then at home to Nottingham Forest.
