Milton Keynes Dons defender Harry Ntimban-Zeh will have nightmares for weeks after playing the lead role in this National Hockey Stadium spine-chiller.
The big centre-half handed Cardiff two first-half goals on a plate, before he was sent off for bringing down Peter Thorne as he raced through on goal after 59 minutes.
Ntimban-Zeh's calamitous mix up with Scott Bevan could have brought the first goal after only eight minutes, but the keeper recovered well to block Alan Lee's effort.
But he didn't heed that warning and went on to gift Cardiff two of the three goals they scored in an explosive eight-minute first-half spell that keeps Lennie Lawrence in a job.
First Ntimban-Zeh hardly got off the ground and allowed the smaller-framed Thorne to head home ex-Don Jobi McAnuff's corner after 14 minutes.
He could not be blamed for Cardiff's second goal, which saw a mazy run and cross from the talented Paul Parry finished well by Lee Bullock after 19 minutes.
But more woeful defending by the big number two just minutes later saw Lee break clean through, and when his effort was saved by the hapless Bevan, Thorne bagged his second of the game from the rebound.
The game was already over at half-time with Cardiff leading 3-0, but Ntimban-Zeh's dismissal shortly after the break turned mission improbable into mission impossible for the Dons.
The Bluebirds laid siege to the home team's goal and it was no surprise when Byron Anthony rose unchallenged to head home Cardiff's fourth goal from Parry's corner after 72 minutes.
Thorne, Lee and Bullock all missed chances to extend the Bluebirds' lead further, before Izale McLeod gave the deflated home fans something to cheer by rifling home a consolation goal after 85 minutes.