Jose Mourinho endured a torrid return to Chelsea, watching his Manchester United side concede a goal after 30 seconds as they slumped to a 4-0 defeat.
The former Chelsea manager received a respectful reception from the home crowd as he emerged into the Stamford Bridge arena prior to kick-off -- but then saw his players fall apart in the opening moments.
Marcos Alonso lofted a pass forward, United defender Chris Smalling left it and Pedro pounced, taking the ball around goalkeeper David De Gea to sidefoot home and score the fastest goal of the season so far.
Shellshocked United briefly threatened to rally when Antonio Valencia crossed towards Zlatan Ibrahimovic, only for the Swede to direct his header over the crossbar.
But the Blues were dominant, with one corner scrambled away from the waiting Diego Costa and Eden Hazard left free to drill another wide from the edge of the area before a quarter of an hour had been played.
And Chelsea got the second goal their pressure had merited with 21 minutes on the clock as United again looked horribly uncertain at the back.
Another corner came off Valencia and then hit Ander Herrera before Gary Cahill smashed a shot in off Daley Blind to put the home side in total control.
It could have been 3-0 soon afterwards but De Gea made a crucial intervention to stop Pedro's cross reaching Costa and another teasing ball from Hazard just failed to fall for the striker.
United again rallied briefly and Chelsea keeper Thibaut Courtois had to be on his toes to stop Ander Herrera's speculative effort from the edge of the box and then block Jesse Lingard's angled follow-up.
Blues defender David Luiz was booked for a high challenge on Marouane Fellaini five minutes before the break, and the teams walked off with Mourinho facing a huge challenge to get anything from his return to London.
The United boss made a half-time change, bringing on former Chelsea midfielder Juan Mata for Fellaini and moving Rashford to a central position alongside Ibrahimovic.
Costa fired home after a deflected shot reached him but was clearly offside and then played a one-two with Hazard, who was unable to reach the return ball under pressure inside the United area.
When a United attack broke down after 56 minutes Moses carried the ball deep into the visitors' half before playing in Hazard, whose effort crashed back off a defender.
Courtois was again on his toes when Lingard tried his luck from distance, parrying the effort, and as the hour mark approached United began to find more rhythm and pace to their passing with Chelsea beginning to sit deeper.
But after 62 minutes the Blues put the game beyond doubt when Eden Hazard was found in the box by an incisive Nemanja Matic pass and steered a clinical low finish past De Gea and inside the far post.
A forlorn-looking Mourinho brought Antony Martial into the action for Lingard, but things went from bad to worse after 70 minutes when N'Golo Kante tricked his way into the area amid more dreadful United defending and slid a low finish beyond De Gea.
Conte brought off Pedro and brought on Nathaniel Chalobah before Pogba fired a speculative effort wide for a thoroughly demoralised United.
A smart turn and shot from Zlatan Ibrahimovic could have brought the scantest of consolations but Courtois again denied the visitors before Moses had an effort blocked as the Blues sought a fifth goal.
Late in injury time, Marcos Rojo was thwarted by the Chelsea keeper as he tipped a powerful strike past the post.