Amad Diallo scored a stunning late hat-trick as Manchester United turned what seemed certain to be a humiliating defeat into a thrilling victory over Southampton at Old Trafford.

United appeared to be heading for a fourth consecutive top-flight home defeat for the first time since 1930 as they laboured badly trying to overcome a Southampton side who had won just once all season and suffered a 5-0 home loss to Brentford on their last league outing.

But Diallo, a week after signing a new five-and-a-half-year contract, had other ideas.

The Ivorian, moved into an attacking role from the wing-back position he started the contest in, took the game by the scruff of the neck, levelling nine minutes from time. He surged into the box, profited from a fortunate break of the ball and drove the rebound past Aaron Ramsdale.

A minute into stoppage time, Diallo kept running on to Christian Eriksen's chipped return pass before beating Ramsdale with a first-time effort.

And he capitalised when Taylor Harwood-Bellis failed to control Ramsdale's pass, nipping the ball away from the former Manchester City defender and passing the ball into an empty net to complete his first senior hat-trick.

"He did a great job. But he has a lot to improve," head coach Ruben Amorim said after the game. "He has the same responsibility as every player who play for Manchester United

"He is in a great moment and he is having a very good season."

It was awful luck on Southampton, who deserved so much more for their efforts but all they had to show was a Manuel Ugarte own goal from a corner.

United, for long periods, showed Amorim was right to express his concerns about his side's effectiveness against lesser opposition after encouraging performances against Liverpool and Arsenal.

But Diallo, who has responded better to Amorim's arrival than anyone else at Old Trafford, was not to be denied and walked away with the match ball in celebration as the home fans cheered him down the tunnel.

It has taken Amorim 14 games to get the full Manchester United experience.

Grinding out a win with 10 men at Arsenal and grabbing a point at Liverpool are all very well but there is nothing like securing a victory in 'Fergie time' - named after United's ability to score late goals under former manager Sir Alex Ferguson - to really know what it means to be in charge of United.

Amorim will know for 80 minutes, his side were absolutely awful.

"It was not a great game," he said. "After Liverpool and Arsenal, I felt the team was a little tired. We were always late, especially in the first half with some problems between the lines.

"But we improved in the second half and they lost some strength because they were doing man-to-man. Then we took control of the game and created chances. You have a feeling that it's going to be hard on them, but we deserved the win."

The former Sporting boss made three substitutions before 53 minutes had been completed. The half-time introduction of Antony, who at £82m has been viewed as the epitome of United's ludicrous recent overspending, for Kobbie Mainoo in a desperate attempt to wrest control of the game told its own story as far as United are concerned.

Yet the grim nature of what was unfolding just kept getting worse.

Within a spell of a couple of minutes, Leny Yoro was completely outpaced by Kamaldeen Sulemana as he sprinted down the left wing. The Southampton man - who gave Yoro a torrid evening - backed himself to finish as he raced into the box rather than pull the ball back to either Tyler Dibling or Mateus Fernandes but fed his shot wide of the far post.

Then United went down the other end, Garnacho cut a cross back to Antony at the far post. All the Brazilian had to do as he slid in was guide the ball into an empty net. Instead, he inexplicably turned it back to Aaron Ramsdale. Replays showed Ramsdale did not actually have to intervene as the ball was rolling wide.

It was shocking stuff and judging by the expression on Sir Jim Ratcliffe's face as he watched on from the directors' box, the profligacy in assembling this group of players was not lost on him.

But even in the depths of despair, as it started to feel as though the relegation battle Amorim spoke about around Christmas could really become reality, United - or rather Diallo - summoned an ending that deserves its place in the annals of historic recent wins.

United have now won two games in a row and have climbed a couple of places in the table to 12th. They still have a huge amount of work to do. But at least they have something positive to remember from this particular night.

For so long, his side did so much right.

"I am from Italy we are the best in the world in mentality and the players they are missing in this," Juric said.

"There is a moment you have to be Italian. Some fouls, we are innocent, like kids playing well and they score. I will show the situation when you do other things. We have to be more evil."

Juric had worked out that United, on their own ground, can be poor against teams they have to make the game against, as Nottingham Forest, Bournemouth and Newcastle have already proved during Amorim's short time in charge.

Had it not been for United keeper Andre Onana, the visitors would have been in front earlier than they actually were.

The returning Cameroon goalkeeper produced an outstanding double save to deny Dibling and then, brilliantly, Fernandes' close-range effort. He had also already produced a low stop to turn away Sulemana's low effort. The Southampton man should then have done better than curl a shot over after he had superbly spun Yoro on halfway and raced unopposed into the penalty area,

Southampton's goal finally came from a set-piece. They had not scored from a corner all season but United are fallible, and have now conceded 10 of their 29 goals from such situations.

The latest was fairly routine and did not look good for Ugarte, given he turned his back as Dibling flicked the ball on at the near post.

As the home side laboured their way through the second half, it seemed Southampton would claim a win to breathe fresh life into their survival fight.

But they could not hold out. There were plenty of positives but the glaring negative remains. Southampton are 10 points from safety with a terrible goal difference. If they cannot win games like this one, when can they?