Manchester United suffered one of their most humiliating defeats in recent memory as rivals Liverpool piled pressure on Ole Gunnar Solskjaer in a 5-0 thrashing which saw Mohamed Salah score a hat-trick and Paul Pogba see red.
United's performance was nothing short of a shambles as Liverpool feasted on some inept defending and questionable tactics, going ahead after five minutes through Naby Keita's low finish having been released through on goal.
Diogo Jota made it 2-0 (13) at the far post from Trent Alexander-Arnold's centre after miscommunication between Harry Maguire and Luke Shaw, before Salah scored for the 10th straight game in all competitions, converting near post from Keita's pass (38).
United were "kidding themselves" by pressing Liverpool, according to Gary Neville on co-commentary after recent criticism at their lack of defending from the front, leaving gaping holes at the back as Liverpool scored a fourth just before half-time through Salah's low, pinpoint finish from just inside the box (45+5). The jeers that greeted Manchester United at the break were ear-splitting.
Salah then completed his hat-trick, touching past David de Gea from Henderson's excellent pass (49), and the hosts went down to 10 men as half-time substitute Pogba saw red for a high tackle on Keita, who was brought off on a stretcher (60).
United somehow saw out the game without more damage, but having conceded 11 goals in three games, and sitting eight points off the top of a Premier League they had promised to challenge for after a busy summer window, pressure on Solskjaer is at an all-time high.
Liverpool move second after a dazzling display, and remain unbeaten since May after Jurgen Klopp's 200th win as manager, reaching the milestone in fewer games than any other Reds boss.
- Player ratings: Salah, Keita 9; Shaw, Maguire and Pogba 2
- Ole Gunnar Solskjaer: My darkest day as Man Utd manager
- Neville on Man Utd humiliation: Pressure will be intolerable
How Liverpool utterly humiliated Man Utd in own backyard
For many, United's comeback victory against Atalanta on Wednesday papered over the cracks, and Liverpool sensed vulnerabilities in Solskjaer's side throughout an embarrassing 90 minutes for the hosts.
But they should have gone ahead on four minutes as Cristiano Ronaldo and Mason Greenwood combined to free Bruno Fernandes on the right of the box, but he opted for power over placement and lashed over with just Alisson to beat.
Keita did what Fernandes couldn't a minute later as United's defence was sliced open all too easily. It's now just one clean sheet in 21 in all competitions as Liverpool countered through Roberto Firmino and Salah, the latter threaded a wonderfully weighted ball into Keita in space in the box, and the midfielder composed himself to slow low past De Gea.
The first 15 minutes resembled a basketball match; Salah found space again but struck wide, then Rashford saw his long-range effort whistle wide, before Liverpool doubled their lead thanks to some woeful United defending.
Shaw and Maguire's mishap resulted in a hashed clearance, allowing Keita to collect possession outside the box, slip in Alexander-Arnold on the overlap, and his centre was converted back post by the unmarked Jota. In truth, Liverpool were queueing up, with Milner behind Jota ready to pounce.
There were still openings for United - Luke Shaw struck just wide from range and Greenwood himself forced Alisson into a save - but their alarming defensive susceptibilities manifested time and time again.
"United have moments of madness in them," said Neville on co-commentary, and that was clear again as a Rashford back-pass from Liverpool's half played in Salah at an angle. He got into the box unopposed, but De Gea blocked him at the last. "They're a crazy team," Neville rightly added.
It got more embarrassing for Solskjaer and United as Liverpool found space in the final third again to score their third. After Maguire blocked Salah's initial shot, the ball squirmed into space for Keita, who squared for Salah to convert at the near post, reacting quicker than both Maguire and Victor Lindelof.
United's incompetence turned to petulance before the break - Ronaldo hacked at Curtis Jones, with Liverpool feeling the yellow he received was too lenient - but it was soon 4-0 as Salah found space on the right of the box again, firing low into the bottom right corner.
United fans let their feelings known at the whistle, booing at length at one of the most one-sided performances seen at Old Trafford in recent decades, with hundreds already leaving the ground.
As the exit gates opened, so too did the floodgates as Salah completed his hat-trick, played through by Henderson as Pogba was caught out in midfield. Salah, regarded as the best player in the world at the moment, nipped in ahead of De Gea for his 15th goal in 12 games this season.
United thought they'd pulled one back through Ronaldo's expert finish after taking on Alexander-Arnold, but VAR intervened and he was found to be offside.
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A horrible day for United had plenty of time to get even worse, and it did on the hour as Pogba's over-zealous challenge on Keita was picked up by VAR - Anthony Taylor showed him red after only 15 minutes on the pitch, but Liverpool's day was soured somewhat by the sight of the impressive Keita being brought off on a stretcher with a suspected ankle injury.
By now, with 25 minutes still remaining, the hundreds on Sir Matt Busby Way leaving the ground had turned to thousands. "Can I go with them?" said Neville.
De Gea's excellent save from Alexander-Arnold's long-range effort kept the score down, then sub Edinson Cavani hit the bar from close range for the hosts, before the nightmare finally ended for United. The party was just getting started for the visiting fans, however.
"Ole's at the wheel," mocked the Liverpool fans throughout the second half, while Jamie Carragher described United as an "absolute mess" after the game. The doubts surrounding Solskjaer's long-term future will intensify as United came firmly second best to their rivals tactically, physically and technically on a humiliating day to forget at Old Trafford.
Ole: Darkest day of career
Man Utd manager Ole Gunnar Solskjaer:
"It's not easy to say something, apart from it's the darkest day I've had leading these players. We weren't good enough individually or as a team. You can't give a team like Liverpool those chances and unfortunately, we did.
"The whole performance wasn't good enough, that's for sure. We've created openings, they've had chances, they've been clinical and we didn't take our chances early on. Then the third goal is the one that decided the game.
"It's mine [responsibly for the loss] - that's it. The coaching staff are brilliant and I chose the way to approach the game and today, we weren't clinical enough going forwards. There were spaces for both teams and when you give good players spaces, they score.
"You can look back at last season when we lost 6-1 to Spurs - this is miles worse. The opposition as well, that makes it miles worse for me as a Manchester lad and we have to get over this as quick as we can and move on."
Klopp: Insane result
Liverpool manager Jurgen Klopp:
"Did I expect that? No. But what we did in the last third was absolutely insane. How we pressed them high, won balls, scored wonderful goals. I actually told the guys at half-time we need to play better!
"The result is insane. It will take a while if it ever happens again. After the game I got told this has never happened before in the long history of LFC and this group wanted to make new chapters for this big history, and tonight was a new chapter.
"But you have to understand these games right. We lost once against Aston Villa, 7-0, or 8-0, whatever, I forget these kind of things very quickly, but it was high. You have to learn off it. We then smashed Crystal Palace once with a similar result, and then…
"When I analyse the game, I cut the goals off and analyse the game. The result is not interesting to analyse. We could play better football than we have to, and we have to stay more concentrated in some moments.
"I couldn't be happier, because it's just incredible being part of this team. Winning 5-0 is exceptional."
Pundits: Pressure on Ole will be intolerable
Sky Sports' Gary Neville:
"The pressure after this game is going to be intolerable in some quarters. The board have made everyone aware that they are steadfast in their support of the manager and that he stays. Results like this undermine that, there's no doubt. This is sobering.
"Manchester United need to change. I believe Ole is going to get the opportunity to change. But there is going to be pressure from every source.
"There's no doubt the manager will get an absolute battering. There will be calls for his head like you wouldn't believe but you wonder what this defeat will do to the players. How will they pick themselves up?
"There's no hiding place after this. United are going to be absolutely demoralised. The next 24 hours is going to be as hot as it has ever been at this football club.
"Am I shocked? Yes and no. I didn't think it would ever get that bad today. This has always been a tight game more often than not but that was a shocker, an absolute shocker - and the timing couldn't have been worse. Because it's been building against what I call half-decent teams and as soon as they've played a proper team, they've been obliterated."
Sky Sports' Jamie Carragher:
"Can I believe what I've seen? No. And I'm not trying to be clever here but I don't think Liverpool were at their absolute best in terms of possession.
"But whenever they got in and around Man Utd's back four... that's just a joke of a back four, the way they're playing at the moment. They were a mess. Keystone Cops defending!
"I think Ole has done a good job but to take on Klopp, Tuchel and Pep, Manchester United need a better manager. I wasn't saying that on Monday in a disrespectful way, I feel for Ole - that will be the darkest day in his career. I don't want to get involved in a slanging match, I know Ole said something back and rightly so.
"I'm not comfortable saying someone should be sacked - but we're comfortable saying Fred isn't good enough or Scott McTominay isn't good enough so I don't feel too bad saying Ole Gunnar Solskjaer isn't good enough.
"Manchester United need a better manager. Ole isn't a manager for Manchester United. He's done really well but you need someone to take them to the next level. Unfortunately, Solskjaer isn't Jurgen Klopp, Pep Guardiola or Thomas Tuchel. It's staring you in the face."
Sky Sports' Graeme Souness:
"I thought Liverpool were fabulous. They were so clinical. They looked like a proper team and they looked like a team with another gear. United were scratching around for a way of playing.
"They have some fabulous players capable of doing great things but they don't do it often enough. They have got lots of problems to solve before they become anything like a proper team."
Manchester United's gruelling run
It does not get much easier; United face a formidable set of fixtures over the next six weeks as they look to keep pace in the Premier League and ensure Champions League qualification, with Chelsea, Arsenal, Tottenham and the Manchester derby looming domestically.
October 30: Tottenham (a) - Premier League, kick-off 5.30pm, live on Sky Sports
November 2: Atalanta (a) - Champions League, kick-off 8pm
November 6: Man City (h) - Premier League, kick-off 12.30pm, live on Sky Sports
November 20: Watford (a) - Premier League, kick-off 3pm
November 23: Villarreal (a) - Champions League, kick-off 5.45pm
November 28: Chelsea (a) - Premier League, kick-off 4.30pm, live on Sky Sports
December 2: Arsenal (h) - Premier League, kick-off 8.15pm
Opta stats: Man Utd's humiliation in numbers
- Manchester United have only lost by a larger margin in this fixture in October 1895 when Liverpool beat them 7-1 at Anfield. It's their largest margin of defeat in this fixture when playing at home.
- Liverpool are only the second team in English top-flight history to win consecutive away games by a margin of 5+ goals without conceding themselves, after Manchester United in February/March 1960.
- Manchester United have lost by a margin of five or more goals at Old Trafford without scoring themselves for the first time since a 0-5 defeat at home to Manchester City in February 1955 under Matt Busby.
- Liverpool have scored 19 goals in their first five away matches in the Premier League this season. In English top-flight history only two sides have scored more after five away games - Manchester City in 2011-12 (20) and Manchester United in 1907-08 (20).
- Manchester United trailed 4-0 at half-time - it's the first time they've ever trailed by four goals after the first half of a Premier League match.
What's next?
Manchester United go to Tottenham on Saturday Night Football in the Premier League, live on Sky Sports Premier League at 5.30pm on October 30, while Liverpool visit Preston in the Carabao Cup on Wednesday night at 7.45pm, live on Sky Sports Football, before hosting Brighton in the Premier League at 3pm on Saturday.