Manchester United manager Jose Mourinho said his players made "incredible defensive mistakes" as he was beaten 4-0 on a humiliating return to Stamford Bridge.
United conceded within 30 seconds as Daley Blind, Chris Smalling and David De Gea all failed to stop Pedro.
Gary Cahill took advantage of poor defending at a corner to make it 2-0 before the break, Eden Hazard added the third just after the hour and N'Golo Kante skipped through for the fourth.
Mourinho told Sky Sports: "In the first minute, you analyse the goal and you see what happened. We made incredible defensive mistakes, individual defensive mistakes, and we paid for that.
"It started bad. After a few seconds, we were losing 1-0. Then you are close to 1-1, and another defensive mistake and it's 2-0.
"Then you are close to 2-1 and they score, 3-0, on the counter-attack. You are close to 3-1 and they score, 4-0, on the counter-attack.
Jose Mourinho said United had to 'keep training and keep fighting.'
"You come with a strategy and you can't concede a goal in the first minute. That changed the game completely."
Mourinho said United had "wanted to create chances and score goals," adding: "In the end, I think [Thibaut] Courtois had more saves than De Gea.
"Every time they went up, they scored. But I told to the players that we should take the risk in the second half even though we know they are very good on the counter-attack."
He later told United's official website: "I have to apologise for that as the leader of this dressing room. But there is only one answer: training and keep fighting."
He said the reception he had received from Chelsea fans on his return to his old club was "fine" but added: "I was not expecting anything different. The crowd behaved in a normal way."
Sunday's defeat leaves United seventh in the Premier League, five points behind fourth-placed Chelsea and fifth-placed Tottenham Hotspur and six points adrift of Manchester City, Arsenal and Liverpool.
Mourinho said: "We play Burnley, Swansea, West Ham. We need now to win matches to close that gap."
Latest Stories
-
IGP shares Easter safety tips on Adom FM’s ‘Ofie Kwanso’
25 mins -
Ebo Whyte offers fully-funded trip as he unveils new play ‘Dubai or No Sex’
36 mins -
Ancient culture of Anlo Kingdom: Exploring “Torkor Atorlia,” the fifth landing stage’s old ways of punishment
51 mins -
Leaders from Saudi Arabia, Turkey, Botswana, Cameroon and Sierra Leone to lead discussions at Africa Finance Corporation’s (AFC) 4th Country & Stakeholder Symposium
1 hour -
Network International Delivers Strong 2023 Revenue growth at 15% y/y and free cashflow growth of 16% y/y
1 hour -
President Akufo-Addo extends Easter Greetings to Ghanaians, urges safe drive
2 hours -
Government pushes for use of more local materials in housing, other infrastructure projects
2 hours -
Dr Bawumia extends Easter greetings to Christians
2 hours -
CAF Confederation Cup: ‘Ghanaians should expect victory against Stade Malien’ – Dreams FC forward Ishmael Dede
3 hours -
CAF Confederation Cup: ‘We want to go there and win’ – Karim Zito on Stade Malian clash
3 hours -
Togbe Adzie Lãkle Howusu XII endorses youth leadership as New Force Movement gains momentum
4 hours -
Public Utility Workers Union appeals to PURC to address power crisis
4 hours -
Anbariya loses another appeal in Kumasi as Appeal Court ratifies High Court ruling against the Islamic Institute
4 hours -
Highway construction health hazard: Ofankor-Pokuase-Nsawam residents appeal for dust relief
4 hours -
SuperJazzClub releases its first single of the year ‘Off’
5 hours