Manchester United boss Alex Ferguson apologised to supporters after Crystal Palace claimed a stunning Carling Cup win at Old Trafford last night.
Substitute Glenn Murray headed a winner in extra-time to send the Championship side through to a semi-final date with Cardiff, at the expense of Ferguson's Premier League champions.
The game had burst into life after 65 minutes when another substitute, Darren Ambrose, opened the scoring with a stunning 35-yard strike, but United forced extra-time with a Federico Macheda penalty four minutes later.
Yet United, showing 10 changes from the side which drew with Newcastle at the weekend, were unable to regain a foothold despite a late rally and Palace deservedly held on after Murray's 98th-minute effort.
Ferguson told MUTV: "I don't know where to start to be honest.
"My apologies are to the fans because that was not a Manchester United performance.
"I don't want to take anything away from Crystal Palace. I wish them every success and hope they get to the final because it was a fantastic, mammoth effort from them.
"Every one of their players worked their socks off to try to get to the semi-final.
"I am just very disappointed."
Murray was close to being offside as he met Ambrose's free-kick for his moment of glory but Palace, who had not scored in their previous five games, deserved their success.
Ferguson said: "When it went to extra-time I thought we must win but it was not to be.
"Obviously the goal was offside - the second goal - from what I have seen.
"We are not getting any luck from linesmen just now but I can't take that away from Crystal Palace.
"They fought hard to get the result and they deserve it."
Palace manager Dougie Freedman was impressed with the way his players acquitted themselves against their illustrious hosts.
Freedman said: "They should be proud of themselves.
"In the last 15-20 minutes of extra time the desire shone through in the end.
"There was no tactical genius. We had to dig in and show that hunger and desire to see the tie through and that is what they have done.
"I felt we had a good gameplan and I thought every single player stuck to our gameplan."
Palace then managed to avoid Premier League big guns Manchester City and Liverpool in the semi-final draw, but Freedman felt Championship rivals Cardiff would be a tough enough test.
He said: "It's probably the hardest draw.
"They are up at the top of the Championship and it is going to be very difficult for us.
"But I am just proud of the lads, to get through to the semi-finals from where we have come from in the last couple of years - relegation zones and administrations."