Two brilliant second-half goals from Wycombe Wanders ensured Dons' winless run continued after a 2-1 defeat in the Leasing.com Trophy.
The game ultimately would mean nothing, with Dons having already secured top spot in the group, while Wycombe would finish bottom. And things looked to be going to form when Brennan Dickenson fired the home side into the lead after 32 minutes with a brilliant free-kick.
Nnami Ofoborh's rocket strike on 58 minutes drew level, before Alex Samuel's strike clattered the crossbar for the visitors. Tempers flared when Kieran Agard was sent off for the second game in a row for his part in a scuffle with Giles Phillips, who also received his marching orders, before Josh Parker's sensational volley in stoppage time snatched all three points for the Chairboys.
With the game a dead rubber, Russell Martin made eight changes to look over some more of his squad for the visit of Wycombe. The only players to survive from Saturday were Callum Brittain, David Kasumu and Brennan Dickenson. Kieran Agard's suspension did not count in the Leasing.com Trophy and thus could start up-front.
With the result being largely irrelevant, the game played out as such with neither side really forcing much of an issue. Hiram Boateng came closest to opening the scoring when he forced a save from Cameron Yates, while at the other end, a mix-up between Baily Cargill and Stuart Moore almost allowed Wycombe a gift of an opener, but the ball was deflected out for a corner.
Brennan Dickenson's Dons career had mixed beginnings, but his first goal for the club was a brilliant one. Coming after 32 minutes, Dickenson's free-kick, 20-yards out, sailed into the top corner to give the home side the lead.
Wycombe looked like a side eager to get back into it in the second period. Substitute Paul Smyth almost made an immediate impact when he tested Moore a couple of minutes after the restart, but there was little the keeper could do to prevent the equaliser 13 minutes later when Nnamdi Ofoborh's fierce volley flew past him from the edge of the box.
Then came one of the misses of the season two minutes later. After Callum Brittain's strike was initially saved by Yates, it fell on a plate to Agard six yards out, but somehow he hit the bar with the net gaping.
Wycombe's Alex Samuel thought he'd given his side the lead when he bullied is way past Cargill in the Dons penalty area, but his strike hit the underside of the bar and bounce away, despite his protests claiming it had crossed the line.
Dons continued to toe a dangerous line and almost let Wycombe in again when they squandered the opportunity to take a shot, but went backwards and allowed Paul Smyth to counter, but his strike was straight at Moore.
Wycombe were lucky not to be reduced to 10 men when Gardiner-Smith hauled down Agard as he closed in on goal, but the striker should have put the game to bed eight minutes from time when he was picked out by Boateng only to see his strike tipped around the post.
As the game raced towards penalties, a flashpoint saw Agard receive a second red card in as many games for kicking out at Giles Phillips, though the Wycombe man was also given his marching orders for retaliating, shoving Agard to the ground.
But into stoppage time, Wycombe snatched the win with another sensational strike, this time from Josh Parker, to secure their only win in the competition.
Referee: David Rock
MK Dons: Moore, Williams, Cargill, Sorinola (Brennan 82), Brittain, Houghton, Kasumu, Boateng, Dickenson (Mason 73), Agard, Asonganyi (McGrandles 62)
Subs not used: Nicholls, Bowery, Mason, Pattison, Freeman
Wycombe Wanderers: Yates, Jombati, Pattison, Kashket (Smyth 46), Mascoll, Phiullips, Freeman, Gardiner-Smith, Samuel (Wheeler 73), Parker, Ofoborh
Subs not used: Allsop, Jacobson, Wheeler, Bloomfield, Thompson
Booked: Ofoborh, Boateng, Dickenson, Gardiner-Smith
Sent off: Agard, Phillips