In the end it was a golden night for Crystal Palace. The Championship side are in the semi-finals for the first time in 10 years, knocking out Manchester United to leave themselves with a last-four tie against Cardiff City and realistic aspirations of reaching Wembley.
This was their first victory at Old Trafford since 1989 and their place in the last four was thoroughly deserved given the conviction and belief that ran through their performance. The visitors played with the togetherness that every giant-killer needs. They never showed any sign of stage-fright, were encouraged by United's shortcomings and refused to be cowed, culminating in the game's decisive moment courtesy of the substitute Glenn Murray's header eight minutes into the first period of extra-time.
Murray struck from close range, turning in Darren Ambrose's free-kick despite the proximity of several United defenders and getting the benefit of the doubt from the linesman despite being marginally offside.
Ambrose, another substitute, had put Palace ahead in the 65th minute, picking out the top corner with a cannon of a shot from fully 35 yards. It was an extraordinary goal that had Gary Neville, in his TV pundit role, wondering whether Old Trafford had ever witnessed a better goal from a side not wearing red. After that United were grateful just to get to extra time.
Federico Macheda supplied their equaliser from the penalty spot, three minutes after Ambrose's opener, but it was typical of the home side's performance that thereafter they seldom threatened to win the game in normal time. The onslaught that might have been expected simply never materialised.
When Ferguson issues a public apology, it has clearly been a desperate night. It has happened only a few times before during his 25 years in charge and it can safely be said that even more was uttered behind the scenes. The manager, in fact, was quite measured in his criticisms, perhaps unwilling to go too far because of the number of young players in his team.
United, however, were abject. The manager may have bigger ambitions, but Ferguson was still entitled to expect much better. United are one of the few clubs not to lower their prices in the Carling Cup, which meant the ground was one-third empty, with large swathes of empty red seats. It was a poor night in more ways than one.
Perhaps, in hindsight, Ferguson may regret giving so many of his first-choice players the night off and playing such an experimental side. The manager reminisced in his programme notes about the time he started the trend: a second-round tie at Port Vale in 1994 that led to a complaint being raised in the House of Commons. On this latest occasion, the one bright spot came in the form of an enterprising substitute appearance from Ravel Morrison, but even that feels like straws-clutching. Nobody from Old Trafford will want to remember this tie.
Macheda was particularly poor, misplacing passes and at one point trying to control a routine ball only to knock it out for a throw-in. He was not alone, however. There was the embarrassing sight of Mame Biram Diouf being penalised for a foul throw. Fábio da Silva picked up a yellow card, could have given away a penalty and limped off injured. Rafael da Silva was also forced off, a sort of deja vu for those who have followed the Brazilians' careers. Dimitar Berbatov will be sent for scans after leaving Old Trafford with a protective cast on a foot.
This is what can happens when Ferguson leaves out Wayne Rooney, Nemanja Vidic et al, installs Jonny Evans as captain and hands out rare starts for the likes of Macheda, Diouf and Darron Gibson. With so many changes, it was probably only inevitable that it would be disjointed at times.
Nonetheless, there were large swathes of the match when the team in red looked strangely devoid of confidence. Several players fell conspicuously short of what would have been expected.
Palace, 12th in the Championship, did not exhibit any nerves. They looked lively, breaking with pace, particularly through Wilfried Zaha, and by half-time it was clear that Dougie Freedman's side sensed an upset.
Morrison's arrival coincided with United's best spell of normal time but it was just as Palace were starting to look vulnerable that Ambrose produced his once-in-a-lifetime goal. The midfielder has always struck the ball sweetly and this one dipped, swerved and arrowed into the top corner.
Palace's lead was short-lived, Patrick McCarthy grabbing at Macheda's shirt to give away a soft penalty. The Championship side did not wilt, though, and at the end the United supporters who had stayed behind clapped the victorious players off the pitch.