Amad Diallo seals Manchester United's latest victory in the derby to surprise City | first division

When Ruben Amorim oversaw their previous victory over Manchester City – with his former club Sporting in the Champions League, was to push the reigning Premier League champions into crisis. That was at the beginning of November and it was City's third consecutive defeat.

Amorim repeated the trick to encourage his new project at Manchester United and leave Pep Guardiola on his knees. There seems to be no way out of the City coach's misery: this is the eighth defeat in 11 games in all competitions, the decline of his conquering team raw and extraordinary.

For a long time, it looked like City would seal a much-needed victory thanks to Josko Gvardiol's header from a corner in the 36th minute. They were meek and insecure throughout, lacking basic drive, but United had no cutting edge. They were dusty in the final third. And then, in the end, they weren't and were able to embrace a result that Amorim will try to use as a touchstone.

It was Amad Diallo, the standout player of Amorim's fledgling tenure, who made the difference. Playing in the number 10 position on the right, Diallo was quick and direct but, above all, he refused to believe that defeat was his destiny. He continued running, always attentive to the possibilities and, after winning the 1-1 penalty – converted by Bruno Fernandes with two minutes left in regulation time – he ran a little more.

Working against Matheus Nunes and between Gvardiol and Rúben Dias, he reached a high ball from Lisandro Martínez on the rebound and the first touch was a wonderful improvisation, up and to the side of the advancing Ederson. He followed up with a volley from a tight angle that squeezed the goal, but Gvardiol was unable to clear from the front of the line.

Nunes, playing as an emergency left back, had conceded the penalty after leaving a pass intended for Ederson woefully short. Diallo intervened, moving away from the goalkeeper and had the presence of mind to pause and deceive Nunes, who had run back, into a rash challenge. Where was City's direction of play?

Diallo has contributed six assists in the league this season (he receives none in the official statistics for winning a penalty), but the goal, his fourth in all competitions, was the one that really left jaws dropping, the one that increased the feeling of helplessness. that has come to affect Guardiola and City.

The game had been framed to some extent by Guardiola debuts on Friday about the idea of ​​losing the locker room. Imagine hearing that at the end of October, when City were unbeaten in all competitions. For the record, he hasn't lost players. There was also the detail about his diet. At night he limits himself to eating soup because his stomach is very upset. Insecurities are everywhere and emerged during a slow derby that, apart from Diallo, had little quality.

Amorim's idea was to be solid; hence Noussair Mazraoui and Diogo Dalot are the full-backs, and Diallo in the most offensive position. The main team news was the exclusion of Marcus Rashford and Alejandro Garnacho from the matchday squad, a decision Amorim indicated was based on what he had seen of them at Carrington, which sounded ominous.

United could sense there were spaces behind City's defensive line and Manuel Ugarte picked out Diallo in the 26th minute, but he went wide. The offside flag was raised. But they were surprised by Gvardiol's goal, which had not been announced. That it came from a corner was sickening and not surprising from United's point of view; They have routinely failed to adequately defend against them all season.

City played short and there was fortune when Kevin De Bruyne's cross deflected off Diallo to advance Gvardiol. But Dalot did not do enough as Rasmus Højlund was absorbed by the ball. Gvardiol was free to direct the header.

The injuries were part of the story. Guardiola was without Manuel Akanji and Nathan Aké, while John Stones was fit to return to the bench. With Rico Lewis suspended, the coach only had three defenders fully available; Maybe seven on the roster isn't enough? That is why he turned to Nunes as a left back, with ultimately disastrous consequences. United would lose Mason Mount after 12 minutes, a huge blow for the unfortunate midfielder.

There was controversy after Gvardiol's goal, Kyle Walker colliding face to face with Højlund after he had fouled the United striker. Walker fell to the ground, an embarrassing attempt by the 93-cap England international to send off his opponent. Both were reprimanded.

United had pace and structure in their passing movements, but had to show more personality and incision. City, meanwhile, were happy to have something to hold on to in the second half. They invited United and if it was strange to see them in such a passive state of mind, creating so little, perhaps they reasoned that United did not have what it took to hurt them.

Diallo extended Ederson with a header and Fernandes had a great chance in the 74th minute after Højlund released him. When his shot went wide and Mount's replacement, Kobbie Mainoo, went under from a free header, it looked like United would fall short. Diallo had other ideas.