Manchester United manager Jose Mourinho blamed "incredible defensive mistakes" for his humiliation on his Premier League return to Stamford Bridge where his former side Chelsea routed his new team 4-0.
Having held out for 90 minutes at Anfield last Monday, United conceded the quickest goal in the Premier League this season to Pedro after 30 seconds and were then ripped apart as Gary Cahill (21), Eden Hazard (62) and N'Golo Kante (70) completed the scoring.
Most of the goals stemmed from poor defending as Chelsea found ever more ingenious ways to inflict pain on Mourinho.
"We made incredible defensive mistakes and you pay for that," he said. "If you score you have a chance and the match would have been different. When you come with a strategy you can't concede a goal like that in the first minute.
"We were coming to have an offensive approach, we wanted to create chances, we showed that after the 1-0. The second and the third were counter-attack goals. If we score a goal like we almost did for 2-1 the game would be different."
Marcos Alonso began the unravelling with a defence-splitting pass between De Gea and his central defenders that found Pedro, while Cahill could not believe his luck when the ball fell to him in the area after Chris Smalling failed to clear a corner. "I couldn't miss from there," said Cahill.
Two up at half time, when United replaced Marouane Fellaini with Juan Mata, Chelsea sat back and waited to hit United on the break with Hazard adding a third after a clever one-two and then Kante driving forward to score his first goal for the club.
That goal would have particularly difficult for Mourinho to stomach because the former Leicester midfielder met so little resistance from those supposedly charged with stopping him getting into the area.
A downbeat Mourinho struggled to find a positive spin to put on a terrible result. It was only the second time in his Premier League career that one of his sides had conceded four goals.
"You lose three points when you lose 1-0 or 4-0, it doesn't make a difference," he said.
"We need to win matches now to close the gap."
Neither Mourinho nor Chelsea manager Antonio Conte would comment on an incident after the final whistle when the stony-faced Portuguese spent several seconds talking in the Italian's ear.
It happened soon after Conte had whipped up the crowd by gesticulating wildly after the fourth goal went in.
Conte shrugged that he was entitled to ask for more noise, adding: "If you want to cut my emotion, then I go home and change my job."
United's misery was completed when Mourinho also revealed that he feared injured defender Eric Bailly, who limped off early in the second half, had suffered serious knee ligament damage.
Earlier Manchester City returned to the top of the standings on goal difference after coming from behind to draw 1-1 with Southampton at the Etihad Stadium.
Pep Guardiola's side, who began the season with 10 straight victories, have now gone five games without a win in all competitions, equalling the Spaniard's worst run as a manager.
It could have been even worse for City after they gifted Southampton the lead when a wayward pass from John Stones put Nathan Redmond in on goal after 27 minutes.
Moments later Stones thought he had atoned by bundling the ball into the net but his goal was disallowed for a Sergio Aguero offside.
Guardiola reacted to the poor first half by replacing De Bruyne with Kelechi Iheanacho, who made an immediate impact by scoring from close range after Fernandinho found Leroy Sane with an exquisite crossfield pass.
Saints remained a threat on the break and Claudio Bravo saved well from Charlie Austin on 74 minutes while Aguero went close at the other end, where Raheem Sterling was a constant threat as City pushed for the elusive winner.