Sir Alex Ferguson has described Manchester United's 6-1 defeat at home to Manchester City as the worst he has experienced in over half a century in the game.
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City took the lead on 20 minutes through Mario Balotelli and that was the difference between the teams at half-time. When Jonny Evans was dismissed shortly after the break, though, the visitors were able to run riot.
Balotelli added his second on the hour and Sergio Aguero made it 3-0 nine minutes later. Darren Fletcher then restored hope in the 81st minute, but two goals from Edin Dzeko either side of a David Silva strike dealt Ferguson his most humbling defeat.
"It was our worst ever day," Ferguson said. "It's the worst result in my history, ever. Even as a player I don't think I ever lost 6-1. That's challenge for me too."
It was Manchester United's worst home defeat since the 1930-31 season, when they were beaten 6-0 by Huddersfield Town amid a run of 12 straight losses in the First Division.
"I can't believe the scoreline. The first goal was a blow for sure but it was retrievable at 1-0. The sending off was a killer for us. We kept attacking when we went 4-1 down and we should have just said: 'We've had our day.'"
Ferguson felt the more experienced players in the team should have realised pressing for further goals was an unwise tactic.
"We just kept attacking. They were attacking three versus two. It was crazy football," he said. "I thought with the experience we've got - Rio Ferdinand, Patrice Evra - they would [defend more] but we just kept attacking. Sometimes there has to be common sense about it. It was a bad day."
He added: "What did concern me was the goals for and against. Goal difference may count. Last year it was in our favour. Most years it is in our favour. This time maybe not."
Despite his immense disappointment, Ferguson feels that the severity of the defeat could prove positive as the club will feel a strong determination to make amends.
"We'll come back. By January we'll be okay. We usually get the show on the road in the second half of the season and that will have to be the case," he added. "We've played all the teams around us and they have all to play each other so the second half of the season is important to us now.
"We will react, no question about that. It's a perfect result for us to react to because there is a lot of embarrassment in the dressing room and that will make an impact."
The scale of the defeat did concern Ferguson, though, as he looked ahead to the potential importance of goal difference as the season progresses.