Sir Alex Ferguson was shocked by the manner of Manchester United's Carling Cup exit at Upton Park last night.
The holders crashed to their worst defeat since 2001 when they were thrashed 4-0 by West Ham, a first loss of the season that ended their 29-match unbeaten run.
Jonathan Spector and Carlton Cole struck two goals each amid a snow storm in east London that failed to dampen the Hammers' determination to reach the semi-finals.
Ferguson was deeply frustrated by United's defending and admitted his side had contributed to their own downfall.
"I didn't expect that, that's for sure. If you analyse it the goals we gave away were absolutely too soft," Ferguson told MUTV.
"We didn't expect that, they were terrible goals for us.
"We had one or two half chances and Gabriel Obertan had a shot saved by the goalkeeper (Robert Green) which then hit the post.
"The goals killed it. You can't just give goals away at this level."
West Ham were incensed to have an early strike by the superb Victor Obinna, who had a hand in each goal, ruled out for offside and Ferguson felt the perceived sense of injustice provided motivation.
"That first goal was a break for them. We were in control in the early part, played some good football. But goals change games," he said.
"The thing that sparked it was the goal that was disallowed because it got the crowd up.
"It was clearly offside because it came off one of their players and went into the net.
"It was clearly offside but they celebrated for so long. It spurred them on."
Spector provided the launch pad for victory with his first goals during his six seasons in English football, both arriving before half time.
West Ham boss Avram Grant hopes the result can help inspire a move out of the Barclays Premier League relegation zone.
"I thought we could win but this is still an unbelievable result. We continue our progress," he said.
"We scored four goals and could have scored more. But for me four is enough.
"To be in the semi-finals is very good for this club. We are trying to build something step by step. We have done the right thing.
"The gap at the bottom of the Premier League was five points and is now three points.
"We have many games left and I'm sure that this shows we can be good in the future."
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