CITY suffered a shock 4-0 defeat by League One leaders Milton Keynes Dons as they exited the Carling Cup at Carrow Road.
A brace from former Canary Luke Chadwick and further goals from Sam Baldock and substitute Daniel Powell gave the Dons a deserved place in Saturday's third round draw - while possible knocks to Wes Hoolahan and Daniel Ayala completed a night to forget for City.
The Canaries will look to put this defeat behind them, dust themselves off and focus on Saturday's Barclays Premier League clash away to Chelsea.
After the game City boss Paul Lambert expressed his disappointment at his side's performance: "Disappointing - really, really disappointing. We got what we deserved which is absolutely nothing and we were never at the races.
"But I can't put my finger on it, the squad was really strong and a lot of them played last year and the start of this season, and we lost to the better side."
He added: "It's probably the first time in two years that I'm really disappointed at what's happened. The first two goals were really poor mistakes but we have to pick ourselves up and go again."
Before the game Lambert did make some changes to his starting line-up as predicted - but it was still a strong City side which took to the field to face the Dons.
Declan Rudd got his first action of the season between the stick while Adam Drury also figured for the first time this campaign at left-back. Russ Martin slotted in at right back, with Zak Whitbread partnering Daniel Ayala in the centre of defence.
David Fox returned to the base of a midfield diamond, with Wes Hoolahan also back in as the offensive midfielder. Korey Smith, another player enjoying his first taste of competitive action this season came in on the right, with Andrew Surman on the left flank.
Up front Aaron Wilbraham was given the nod against his former club, joined in attack by Simeon Jackson.
Play was even in the opening exchanges with chances at a premium, though first Ayala and then Drury had to be alert to make important blocks to keep out the highly-rated Sam Baldock.
But they could do nothing to stop the League One leaders taking a shock lead in the 21st minute, Gleeson capitalising on Ayala's mistake before finding Chadwick in the box and the former Norwich man slotted home coolly past Rudd.
Seven minutes later things turned from bad to worse as another defensive lapse, this time from Drury saw him robbed of the ball by Gleeson and his pass set Baldock free to advance on goal and then fire home past Rudd with a great finish to make it 2-0.
City were struggling to find a route to goal at the other end, although Drury's fiercely-struck cross in the 38th minute after a neat bit of control did swerve goalwards and force David Martin to make a save, while Jackson's shot deflected behind two minutes later as the Canaries attempted to get a goal back before the break.
Half-time: Norwich City 0, MK Dons 2
During the interval the Dons made a change as Ibehre was replaced by Angelo Balanta.
A few minutes after the break David Fox tried his luck with a 30-yard free-kick but his low effort fizzed past the post.
In the 50th minute we saw the game's first yellow card as Shaun Williams was cautioned for a heavy challenge on Wilbraham in the centre circle.
Two minutes later we saw the best effort yet from City as Andrew Surman showed good positivity to take on a shot from 27 yards which dipped wickedly and forced Martin to tip over acrobatically.
But on the hour City's improved second-half showing was knocked off the rails as the Dons broke with an incisive move which ended with Chadwick in behind the defence and lifting the ball over Rudd for his second and the visitors' third of the night.
Both sides made substitutions on 63 minutes, Steve Morison coming on for Hoolahan for the Canaries and Bowditch making way for Daniel Powell for the visitors.
And Powell had only been on the pitch for five minutes when he compounded the misery for City with a fourth goal in the 68th minute, the City defence caught at sixes and sevens, allowing the Dons sub in behind to blast the ball home past the helpless Rudd.
In the 70th minute City made another change as Simon Lappin came on for Whitbread and four minutes later Wilbraham had a half-decent effort for Norwich, hitting a half-volley just wide.
There was another blow for the Canaries on 77 minutes as Daniel Ayala limped off to be replaced by Ritchie De Laet.
Norwich City: Rudd, R.Martin (c), Drury, Whitbread (Lappin 74), Jackson, Surman, Hoolahan (Morison 63), Fox, Smith, Wilbraham, Ayala (De laet 77). Subs not used: Ruddy, Johnson, Holt, Bennett.
MK Dons: Martin, Smith, Lewington (c), Mackenzie, Gleeson, Potter, Bowditch (Powell 63), Baldock (O'Shea 77), Williams, Ibehre (Balanta 46), Chadwick. Subs not used: McLoughlin, Chicksen, Flanagan, Baldock.
Referee: Mr M.Haywood