Pep Guardiola's side looked to be in cruise control when Erling Haaland scored in the 53rd minute to put City up 3-0 at home against Feyenoord in the Champions League.
But in the space of 14 staggering minutes, Feyenoord had equalised thanks to David Hancko in the 89th minute, sending the Etihad into a stunned silence aside from the pocket of travelling fans.
Although the 3-3 result snapped a five-game losing streak for City across all competitions, blowing a three-goal lead will have felt like a defeat for Guardiola and his troops.
Reacting on talkSPORT's Sports Bar immediately after the contest, Cundy and ex-Tottenham midfielder Jamie O'Hara couldn't believe the capitulation that had just transpired.
"It's a stinker, that," O'Hara said.
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"3-0 up? What are they doing?"
Cundy added: "Tonight, wheels have come off.
"Look, Spurs were brilliant on the weekend. City were terrible, they got turned over in the Premier League.
"3-0 up against Feyenoord with 15 minutes to go? And you draw 3-3? Wheels have come off. That's it."
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Some fans will point out City look a completely - and not for the better - team without Ballon d'Or winner Rodri in their midfield.
However, given Rodri tore his ACL against Arsenal in September, O'Hara wasn't having that excuse any more.
"It can't just be about Rodri," O'Hara said.
"We've got past that now. There's something going on at Manchester City that no-one seems to have the answer for."
Cundy then delivered a brutal dissection of just what had gone wrong for City, with plenty of warning signs presenting themselves during a 4-0 loss to Tottenham last Sunday.
"They are so open," Cundy said.
"Their press, there is no joined-up thinking. Pep has signed a new deal, which is good for City.
"But right now, this is probably going to be his biggest job ever in management to turn this around. They are a mess.
"I'm watching Man City against your lot (Tottenham) on the weekend. I'm watching Spurs bop the ball around deep in their own half. Not only that, Spurs get out, there's an overload, three versus one, on the right-hand side. How is that happening? That never happens.
"Spurs were magnificent. City, terrible. Watching tonight, they don't look comfortable at 3-0 up. How can that happen?
"The wheels have come off tonight, officially. Spurs at the weekend, they were wobbling. Tonight, the wheels have come off."
O'Hara noted that with City's dreadful run of form, 'Liverpool must be licking their lips.'
As it stands, Premier League leaders Liverpool hold an eight-point advantage over second-placed City.
That gap could easily become 11 when Arne Slot's side welcome a battered and bruised City to Anfield on Sunday.
If Liverpool can snag three points from that contest, it could lead some to boldly declare City have too much ground to catch up in the race for the Premier League title.
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Should City lose to Liverpool on Sunday, they may end the weekend as low as fifth given Chelsea, Arsenal and Brighton are all on 22 points.
Safe to say, there will be a lot of soul-searching among Guardiola and City's stars before that match as they look to snap a six-game winless streak.