Manchester United midfielder Youri Tielemans has admitted his side were "careless" and not good enough in the derby defeat to City.
Refereeing decisions dominated the headlines after Manchester City's 1-0 win at Old Trafford on Sunday in the fourth round of the Premier League.
Phil Foden's sending-off in the 23rd minute sparked widespread controversy. The only goal of the match, scored by Erling Haaland, proved just as contentious. Enzo Fernandez was clearly offside in the build-up, yet the goal stood, and officials later admitted an error and that it should have been ruled out.
United feel great anger at the decision, but Tielemans conceded his side did not do enough while they held a numerical advantage for a long spell.
The Belgian told NBC Sports: "First and foremost, we should not have conceded the goal, but if it hadn't been given, it would have been a different match."
He added: "I don't think we created enough chances to win the game anyway. I think we were a little bit careless in dealing with the ball, and perhaps we didn't make the right decisions in the final ball."
As reported by English newspaper "Metro", he continued: "It's disappointing, everyone feels disappointed and frustrated because we know we can play much better."
He went on: "We want to do things well, but today it didn't happen the way we wanted."
He concluded: "We didn't exploit the spaces in the best way, we made mistakes in our passing, and perhaps we were a little hasty. We didn't play the right final pass in the final third of the pitch to create enough chances to score."
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