Manchester United crumbled to a humiliating 3-0 defeat against Bournemouth at Old Trafford to leave manager Erik ten Hag under mounting pressure.
Ten Hag's side came into the game hoping to build on Wednesday's 2-1 win over Chelsea but fell behind to Dominic Solanke's fifth-minute opener before capitulating in the second half.
Andoni Iraola's in-form side extended their lead through substitute Philip Billing's header and Manchester United's afternoon got even worse when Marcos Senesi nodded in the third from a corner.
Manchester United's shambolic defensive display was compounded by a limp effort in attack as they registered only three shots on target, with the home fans loudly booing their seventh Premier League defeat of the season at the final whistle.
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The loss sees United lose further ground on the top four, while Bournemouth celebrate a historic win - their fourth in five games and first ever at Old Trafford - which moves them up to 13th in the Premier League table, 10 points clear of the drop zone.
How Bournemouth stunned woeful Man Utd
Any hope that Manchester United might carry some momentum into the game following their win over Chelsea swiftly disappeared as Bournemouth pounced on their sloppy efforts to play out from the back to stun Old Trafford with the opening goal.
Lewis Cook was the creator, showing fine anticipation to reach an undercooked pass by Bruno Fernandes before Scott McTominay. He then charged past Sofyan Amrabat and crossed for Solanke, who expertly flicked home his eighth Premier League goal of the campaign using the instep of his right boot.
Manchester United dominated possession and created half-chances in response, but a looping Harry Maguire header pushed over the bar by Neto was their only shot on target in a poor first half.
At the other end, they continued to look bewilderingly open and were fortunate not to fall further behind.
Marcus Tavernier had a chance to double Bournemouth's lead when he cut inside and shot too close to Andre Onana. Solanke went even closer when he struck the post following a rapid attack after a loose pass from Scott McTominay in midfield.
Manchester United showed some glimmers of improvement after half-time, with Anthony Martial suffering the ignominy of hearing cheers when his number went up to be replaced by Rasmus Hojlund, but they continued to labour in front of goal.
Bournemouth defended heroically, throwing bodies in front of shots, and again demonstrated their huge threat in transition for their second, with Solanke charging forward and feeding Marcus Tavernier, whose far-post cross was powered home by Billing.
That goal came against the run of play but there was no way back for the lacklustre hosts and soon the situation got even worse for them, loud boos from the home fans drowning out the cheers of the delirious travelling supporters when Senesi headed in Tavernier's corner for the third.
It was no less than Bournemouth deserved and they thought they had a fourth goal when substitute Dango Ouattara bundled home following yet another Manchester United error, this time from Maguire, only to be denied by VAR due to handball.
The stands were already emptying out by that point as furious home fans made for the exits, but there were still plenty left behind to greet the final whistle with loud boos.
Their misery was further compounded by a petulant booking for Fernandes which ensures their captain will be suspended for next weekend's Premier League showdown with Liverpool at Anfield.
Ten Hag bemoans Man Utd mentality
Man Utd boss Ten Hag said: "We started very poorly. There was I think a big difference, I think, to Chelsea when we started the game very well and we were very aggressive and very focused. Today, we were not."
Of conceding so early, Ten Hag said: "It was our fault in the build-up. We knew they were aggressive in the pressing. You shouldn't give away the ball so easily. Then, defending in transition, we gave them too much space.
"It's a good goal from their side, but from our side you can't be starting like this. You have to get a better position and it all has to do with focusing."
He added: "I refer to that game from Chelsea. You have to be at your best in every game. That demands a lot of energy, starting with the right focus. When you start like we did, you can't do it. You get killed.
"It was a good opponent, they played very lively and very dynamic. So, credit to them. But we have to do things better.
"You have to deliver every day. That demands a mentality, so you have to bring it. We have to change that."
Sherwood: Man Utd threw the towel in
Watching on in the Soccer Saturday studio, Tim Sherwood accused Manchester United's players of throwing the towel in during the second half.
"I think the performances have been as bad as this, but they've got away with it," said Sherwood. They improved against Chelsea because they didn't have to take the game to the opposition. They could play counter-attack football.
"There's nothing wrong with being a counter-attacking side but when a team wants to sit back, you have to find a way of opening them up. They are devoid of anyone with any imagination or creativity apart from Bruno.
"But if you have Bruno in your team, he is not going to work back. Amrabat is left on his own in there and hasn't got the legs.
"Credit to Bournemouth. They had a gameplan and pounced on it and were clinical in their finishing. But very rarely was I off my chair thinking Manchester United must score here. Bournemouth were quite comfortable.
"We're talking about a team in 16th going away from home to Old Trafford. I'm within my rights to think Manchester United, with world-class players and the money they've spent, should be able to break them down and score.
"But they got worse. In the second half, they came out and it looked like they had thrown the towel in, which is unfortunate for their fans watching on.
"At the moment, I cannot see Manchester United getting into the top four this season with performances like that."
Solanke: Magificent win shows our direction
Bournemouth goalscorer Dominic Solanke said: "Magnificent. To win away at Old Trafford is touching for everyone really.
"One of the best stadiums in the world and one of the best clubs in the world so to come and win the boys are delighted."
"I'd probably say [it's one of the best results in our history] and it shows the direction we are going in. I think we have been building a lot in the last few weeks we are feeling confident we are feeling great.
"At the moment we feel like we can beat anyone and that showed today. I think just composure really. The stadium is magnificent. It's easy to probably get intimidated here but we kept our heads.
"We were confident on the ball kept playing and attacked when we could and kept pressing through the whole game. We are just delighted to get the result.
"I think we've just started clicking. A new manager, obviously coming in to the team. At the beginning we were still trying to kind of find our feet with a new philosophy.
"We've definitely started gelling in the last few weeks and it has showed on the pitch."
Story of the match
Man Utd's unwanted record - Opta stats
- This was Manchester United's heaviest Premier League home defeat against a side starting the day in the bottom half of the table.
- Bournemouth earned their first away win against Manchester United in all competitions, having drawn one and lost nine of their 10 previous visits to Old Trafford.
- Manchester United have conceded three or more goals in five different home games in all competitions this season. The last time they did so in more different games at Old Trafford was in 1962-63 (six).
- Since their first league win of the season on October 28, only Liverpool (17) have earned more Premier League points than Bournemouth (16 - Arsenal on 15 before their meeting with Aston Villa).
- Manchester United have lost six of their last 11 home games in all competitions (W5), as many as in their previous 57 at Old Trafford.
What's next?
Manchester United must beat Bayern Munich at home on Tuesday December 12 and hope Galatasaray draw at FC Copenhagen to qualify out of Group A in the Champions League. Kick-off 8pm.
United then visit Liverpool in the Premier League on Sunday December 17, live on Sky Sports. Kick-off 4.30pm.
Bournemouth host relegation rivals Luton on Saturday December 16. Kick-off 3pm.