Amad Diallo inspired Manchester United to a 2-1 comeback derby win at the death as Ruben Amorim piled more misery on Pep Guardiola’s malfunctioning Manchester City.

All eyes were on the Etihad Stadium as the Portuguese led the Red Devils across town for the first time to take on a side that he last month stunned in his penultimate match as Sporting Lisbon manager.

Things have gone from bad to worse since then, with Diallo the hero on Sunday as Amorim inflicted City’s eighth defeat in 11 matches as the worst run of Guardiola’s managerial career continued.

Josko Gvardiol’s header had put the champions on course for a much-needed win as United’s corner issues were exposed again, but the visitors dug deep to win like they did at Viktoria Plzen in the Europa League.

Matheus Nunes, who had been playing as a makeshift left-back, gave away the ball and then clumsily brought down Diallo in the box, resulting in Bruno Fernandes levelling from the spot two minutes from time.

There was still more drama to come as the Ivory Coast international raced onto a Lisandro Martinez pass, lifted the ball beyond Ederson and then scored a 90th-minute winner from a tight angle.

It was quite the turnaround from a side that had been staring down the barrel of a third straight Premier League loss in a single season for the first time since 2015.

Instead, questions over the eye-catching decision to omit Marcus Rashford and Alejandro Garnacho from the matchday squad and the all-round display will be largely replaced by reflections on a big win.

City only had three senior defenders available, meaning Nunes lined-up at left-back against a United side forced into an early change after Mason Mount pulled up.

The midfielder looked devastated as he had to be replaced by Kobbie Mainoo in the early stages of a match that continued in even fashion.

The first shot either side managed came off the left boot of Phil Foden from 20 yards in the 21st minute and Ruben Dias powered a header over after the City player saw another attempt blocked.

United seemed content with the pattern of play and had their best chance in the 26th minute, but Diallo slammed wide of the near post unaware he had strayed offside when sent scampering through.

Amorim’s men could only muster half chances and their soft underbelly from set-pieces was exposed in the 36th minute.

Kevin De Bruyne played a corner short to Ilkay Gundogan and collected a return pass, before seeing his cross deflect off Diallo and met by a thundering Gvardiol header past Andre Onana.

The opener ratcheted up the tension inside the Etihad and tempers soon frayed, with Rasmus Hojlund enraged by a Kyle Walker foul and putting his head into that of the City captain.

The defender dramatically fell to the ground attempting to get the United striker sent off, leading players from both sides to clash and the pair to be booked.

Foden wriggled to get away a deflected shot that forced a good low save from Onana as City sought a second before the break.

City survived a disjointed start to the second half as United failed to punish some errant passes and poor decisions.

Amorim’s men continued to edge possession but offered little by way of attacking threat until Diallo saw a header clawed away by Ederson in the 62nd minute.

Two minutes later Hojlund went down in the box after a challenge by Dias, but referee Anthony Taylor and the VAR deemed it to have been normal contact.

De Bruyne blasted narrowly over after United failed to deal with danger and Amorim held his head in his hands in the 74th minute after Fernandes lifted wide of the far post having been put in by Hojlund.

Amorim attempted to alter the dynamics as the match looked beyond them, only for Nunes’ late wobble to swing things.

The Portuguese’s under hit back pass was cut out by Diallo, who took the ball wide beyond Ederson and decided against shooting as he weighed up his options. Nunes’ attempt to make amends saw him clatter into the forward, leading to a penalty that Fernandes scored in the 88th minute.

Things got worse for flat-footed City in the 90th minute. Martinez floated a ball over to Diallo, who took a touch over Ederson and squeezed home from a narrow angle to spark bedlam in the away end.