Bournemouth victory leaves Manchester United in Premier League's bottom half at Christmas
The Red Devils have never been below 10th in the league table at Christmas before
Ruben Amorim's Manchester United staggered into Christmas on the back of a chastening 3-0 home loss to an impressive Bournemouth side that now are up to fifth in the Premier League standings.
A year after securing their first ever victory at Old Trafford, Andoni Iraola's Cherries triumphed by the same scoreline as they inflicted the biggest blow of the Portuguese head coach's short reign.
Dean Huijsen became the latest player to capitalise on United's lax set piece defending, before a Justin Kluivert penalty and Antoine Semenyo strike sealed a stunning win that brought boos from the home fans at full-time.
The result leaves the Red Devils marooned in 13th over Christmas and marked an alarming drop in performance and spirit from last Sunday's 2-1 derby win at Manchester City.
United boss Amorim had always warned there would be bumps in the road but this fourth defeat in his ninth match in charge further underlined the issues at hand.
As for Bournemouth, chants about European tours filled the air as Iraola saw his side silence Old Trafford for the second straight season.
Marcus Rashford's absence from a third consecutive matchday squad had dominated the pre-match discussion as Amorim made six changes following the chaotic Carabao Cup exit at Tottenham.
Amad Diallo was among those restored to the starting line-up and the livewire saw an early snapshot stopped by Kepa Arrizabalaga, but Bournemouth looked more confident and coherent in cold, biting wind.
Semenyo's strike straight at Andre Onana was the best the visitors could muster early on but United offered little more before an all too familiar weakness in United's armoury was exposed.
Tyrell Malacia was furious to be adjudged to have fouled Adam Smith and Huijsen easily beat Joshua Zirkee to head home the resulting free-kick from Ryan Christie in the 29th minute.
There were groans after Evanilson produced a hopeful acrobatic attempt shortly after - but United showed flickers of life before the break.
Bruno Fernandes slammed a great chance narrowly from a Diallo cutback before Huijsen twice threatened to undo his good work.
First the defender's nonchalant pass was cut out by Kobbie Mainoo, who broke and played in Fernandes to get away a shot that Kepa saved well.
The ball ended up going out for a corner, with unsighted Huijsen directing Diallo's corner millimetres wide of his own goal.
Fernandes drove wide from distance and Mainoo struck wide after a battling run before the break.
Amorim brought on Leny Yoro for Malacia at half-time and soon made two further changes, with Rasmus Hojlund and Alejandro Garnacho replacing Zirkzee and Manuel Ugarte.
Those changes came just before a corner that caused problems at the back, forcing Lewis Cook - Bournemouth's own half-time introduction - to hack clear.
The dynamics would soon change in the visitors' favour after Noussair Mazraoui brought down Kluivert in the box. Referee Craig Pawson immediately pointed to the spot and the Netherlands international stepped up to send Onana the wrong way as he stroked home in the 61st minute.
Things went from bad to worse two minutes later.
Mainoo saw a ball cut out and Bournemouth break broke as Evanilson slipped in Dango Ouattara, whose cutback was driven home by ever-improving Semenyo to make it 3-0. The elated Cherries fans bellowed: "Man United, it's happened again."
Amorim's side were rocked but attempted to retaliate. Garnacho was sent racing through by Hojlund but could not beat Kepa, who then produced an excellent stop to deny the Denmark striker.
Diallo slammed wide and Milos Kerkez went close to a fourth for Bournemouth as Old Trafford began to empty.
Yoro saw a shot blocked on the line in stoppage time but it would have been scant consolation as boos greeted the final whistle from the United fans that stayed until the bitter end.