Former Manchester United captain Roy Keane has slammed the Red Devils for their performance in Sunday's Manchester derby, calling the heavy defeat to Manchester City "hugely embarrassing".

The 20-time English champions entered the contest off the back of four straight Premier League victories, but they were comfortably beaten by the Citizens, who scored six times on home soil.

Man United did give their fans something to cheer late on with a couple of goals from Anthony Martial, but Keane has said that the result is "a huge step back" for his former side.

Erling Braut Haaland and Phil Foden both scored hat tricks for Pep Guardiola's team, who are now one point behind Arsenal at the top of the Premier League table.

"Man City were magnificent. Watching Man City, it is a pleasure. Watching them live, they are one of the best teams I've ever seen," Keane told Sky Sports News after the match.

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"But Man United, [it's] a huge setback for them. We were giving them a little bit of praise over the last few weeks, but this is a huge step back. Four-nil down at half-time - they were 4-0 down at Brentford - and the performance in the second half, it's no good, even as consolation. They scored a few goals - the game's over.

"There's nothing for Man United to take out of this game. From the players' point of view, they really should be embarrassed. You can't go in at half-time 4-0 down in a derby game, it's hugely embarrassing.

"Haaland and Foden were brilliant, but if they're getting the service from people like De Bruyne and you're giving him time and space, you're looking for trouble, and they got punished and rightly so.

"This game is brutal. When you're not quite at it, you get hammered by your local rivals. They should be embarrassed. I just can't imagine going into a dressing room at a big club like Manchester United and you're 4-0 down at half-time.

"It must be bizarre - but saying that, they must be getting used to it because they did it at Brentford. The manager must be scratching his head with his staff and thinking, 'We've made progress over the last four games'. Huge setback."

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Meanwhile, former Man United defender Gary Neville claimed that the Red Devils "froze" in the Manchester derby under pressure from their rivals.

"The story of the game is that in the first half Manchester United froze. There's no doubt they bottled it. There has been promise in the last few weeks from United. But this is a reminder of how far behind they actually are the best team in the country," he added.

"They have been really nervous. They have just not handled this derby at all. I expected so much more from United. There was no composure. They never settled. They were anxious and nervous on the ball."

Man United will now switch their attention to the Europa League, facing a trip to Cyprus to take on Omonia, while they will be back in Premier League action against Everton on Sunday.

Raphael Varane has emerged as a huge doubt for the team's upcoming matches due to the ankle problem that he picked up in the first half of the contest on Sunday.