Erik ten Hag said he was “surprised” by his team’s performance during their 6-3 derby loss to Manchester City, and questioned why his players had shown a "lack of belief".
The derby could not have started off worse for United, with City scoring four goals in the first half, two each from Phil Foden and Erling Haaland.
Antony got one back in the second half before Haaland and Foden completed their hattricks.
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United then scored two consolation goals late on through Anthony Martial.
Speaking to Sky Sports after the defeat, Ten Hag said: "I am surprised why we didn't bring it on the pitch.
"It’s four weeks ago [United’s last league game], but I have seen a different team, a different spirit and a different vibe. Today we were not convincing, we were not on the front foot and we were not brave in possession.
"I will show the team tomorrow we could have been on the front foot. In the first goal, we won the ball and could have created a chance and gave it away. That is unacceptable."

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When asked why things had gone so wrong, Ten Hag responded: “It’s difficult to find out [what happened] straight after the game. I need to talk to my players. They know they can do better. If you don’t fight, and we didn’t, you’ll get a problem against a team like Man City.
“I don’t think you can compare this [to the Brentford game]. Against Brentford, we didn’t run; today, we didn’t follow the principles; we were indisciplined. Once again, it was a lack of belief.”
Despite City’s scintillating display, the Dutch manager emphasised that his own’s side performance was the main reason for the loss.
“When you don't believe on the pitch, then you can't win games, that is unacceptable. We get undisciplined at following rules, and you get hammered, that's happened today.
"For me, it was a surprise. We were not on the front foot, we were not brave on the ball, and there were spaces to play, but we were not brave enough.
"All the credit to City, but it's nothing to do with City, our performance was not good. It had to do with the belief as individuals and as a team.

MANCHESTER, ENGLAND - OCTOBER 02: Phil Foden of Manchester City celebrates their sides fourth goal with team mates Sergio Gomez and Erling Haaland during the Premier League match between Manchester City and Manchester United at Etihad Stadium on October 0

Image credit: Getty Images

"From the first minute I felt it, and at half-time, we changed things, and we changed attitude. We saw a different Manchester United after half-time, and we scored goals, we created some more. On the ball we were more brave, we came in the opponent's half, and we scored three goals.
"In this moment I can't think about positives. We let our fans down, we let ourselves down and we're hugely disappointed."
Christian Eriksen also spoke to the media after the match, saying that the defeat “came very heavy.”
“Everyone feels it was a very bad day at the office," the Dane said. "We started on the wrong foot. They had chances straight from kick-off. We can only blame ourselves.
"We missed a bit of courage to play out from the back, and we let them be at their strength. The main focus from this game will be on ourselves.
"There are a lot of things we need to change and a lot of things we need to do better. Today was far from acceptable from what we should be doing."
Ten Hag will hope that he can shape up his team in time for their mid-week Europa League match against Omonia before they face Frank Lampard’s Everton on Merseyside next weekend.
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