The moment despair and disillusionment turned into anger was marked by a sound. Eastlands had endured the gloating of the Nottingham Forest supporters better than most football crowds but then something snapped in some of the Manchester City fans. They joined the visitors in singing "You'll be sacked in the morning".
The object of their scorn was their manager Mark Hughes. This is January, the promised month City have been waiting for since the Abu Dhabi owners landed in Manchester to make the club the richest in the world. The transfer window was a fantasy land populated by exotic players and expensive purchases, and there on the pitch that dream was laid bare. The reality was that a club whose gaze had lifted towards the Champions League places in August, were being knocked out of the FA Cup by a Championship team. At home.
The boos poured from the stands aimed at the players but principally at Hughes, who had presided over an embarrassing performance. At 3pm the future had appeared bright as Wayne Bridge, an £11m signing from Chelsea, was paraded before the crowd. At 5pm the present was a ruin and the City manager was talking of needing "four or five players" to turn the side into a consistent force.
Out of the FA Cup, one win in nine matches, two points above the relegation places in the Premier League, the evidence presented in this tie was that this is an under-estimate.
"The reaction of the crowd was understandable. I have no problems whatsoever with that because I understand their frustration," Hughes, who had spent more than a hour in the post-match dressing room angrily expressing his own feelings, said. "We're all extremely disappointed and we understand that the performance we produced is not acceptable. At the moment we're frail, we lack a physical presence."
The City fans' reaction to that would be "why"? Hughes could have bought a defensive midfielder in the summer but failed to do so. The mitigating circumstances of the absence of Robinho and Stephen Ireland and the hamstring injury to Shaun Wright-Phillips that will sideline him for four weeks ring hollow in supporters ears when this is borne in mind.
City plan to spend up to £60m this month but the feeling running freely round the Eastlands stands is that Hughes should not be the man to spend it. Not when the current squad seem bereft of spirit. Forest, in a relegation struggle of their own in the Championship and with their new manager Billy Davies in the stands prior to starting work today, won because of the simple virtues of hard work and belief. They did not kick City out of their rhythm, they applied themselves harder.
"They worked extremely hard," Hughes conceded, "ran around, made it difficult and forced us into errors. Once they got their noses in front it made it more difficult for us. But we didn't have that creative spark and if we haven't got that it's very difficult to unlock the door."
It is even harder to find the key if your side is full of accidents waiting to happen and no-one personifies that more than Micah Richards. When he made his international debut in November 2006 he was a force of nature set to be an England fixture; now he is making a mistake almost every time he appears. In this game it was a weak, unchallenged header, to the edge if the area from where Nathan Tyson smashed a volley to put Forest ahead.
Richards's error was matched by Pablo Zabaleta en route to Robert Earnshaw getting the second and when Dietmar Hamann gave Joe Garner a free route to goal with a ridiculous throw-in, City's disintegration had taken on comical proportions.
"I've no idea," Hughes said when asked to explain Hamann's thinking. "Didi is an experienced player and if you asked him why he did it he wouldn't be able to explain it either.
"These things happen in games and we were punished for it. I was more concerned with the rest of the game rather than the individual errors. Those hurt us but it was the performance that concerned me. I'm disappointed because I know we're capable of much better and we didn't produce it. It's a rollercoaster. We're in a trough this week, no doubt next week we'll be on the crest of the track. At the moment I don't know what they're going to produce."
Forest's coach John Pemberton, in temporary charge, said his players had been given simple jobs and they had undertaken them to the letter. "It's dream stuff," he said, before pondering the next, more mundane, task of plotting the downfall of Lincoln City's reserves.
At least Pemberton knows his future. Can anyone say the same for Mark Hughes?
Goals: Tyson (38) 0-1; Earnshaw (42) 0-2; Garner (75) 0-3.
Manchester City (4-5-1): Hart; Zabaleta, Richards, Dunne, Ball; Wright-Phillips (Vassell, 24), Kompany, Fernandes (Hamann, 60), Elano, Caicedo (Jo, 70); Sturridge. Substitutes not used: Schmeichel (gk), Garrido, Clayton, Berti.
Nottingham Forest (4-5-1): Smith; Chambers, Morgan, Breckin, Cohen; McGugan, Anderson, Thornhill, Perch (Wilson, 18), Tyson (Davies, 81); Earnshaw (Garner, 73). Substitutes not used: Richardson (gk), Byrne, Heath, Reid.
Referee: L Probert (Wilts).
Booked: Man City Dunne
Man of the match: Thornhill.