Peterborough United suffered penalty shootout agony as they were dumped out of the Leasing.com Trophy by Ipswich Town on Wednesday night.
Posh were the better side over the 90 minutes and created more chances, but they couldn't make their superiority count as they drew 1-1 with their Sky Bet League One rivals.
That meant it was a penalty shootout, and after Adam Przybek made saves from Siriki Dembele and Frankie Kent, it was Ipswich who triumphed 6-5 to move into the last 16 of the competition.
In normal time, teenager Ricky-Jade Jones was the man on target for Posh, levelling after Idris El Mizhouni had fired the visitors in front.
Posh boss Darren Ferguson made nine changes to the starting line-up from 3-0 FA Cup second round win over Dover Athletic.
Dan Butler and Joe Ward were the only players to keep their place, while Siriki Dembele returned from injury, with teenager Ricky-Jade Jones also starting.
The big striking guns of Ivan Toney and Mo Eisa were named on the bench.
Ipswich, who drew against Coventry City in the Cup at the weekend, made 11 changes.
The selections of both managers made it pretty clear where this competition lies in their list of priorities this season.
Not only was there nine changes made by Posh, there was a change of formation as well, to 3-5-2, with Butler, Rhys Bennett and Niall Mason the back three, and Ward and Idris Kanu the wing-backs.
Serhat Tasdemir was the most advanced of the central three, with Alex Woodyard and Kyle and Barker behind him, with Dembele and ones were up front.
There was an open start to the game, but it was the 11th minute before a keeper had to make a save, and it was Ipswich's Adam Przybek who got down low to his left to smother a Serhat Tasdemir effort.
On 17 minutes he had to react a little sharper as Butler's stinging effort from 25 yards was curling into the bottom corner, but Przybek palmed it away, and moments later he did well to stop a piledriver from Joe Ward, after he had cut in from the left wing.
Ipswich had barely mustered an attack of note, but on 23 minutes they were ahead, and it was a defensive calamity for Posh.
Mason's square ball to Barker in the centre circle was cut out, and Ipswich took full advantage.
They broke at speed and opened up a chance for James Norwood to shoot from 20 yards, and although his effort was saved by Aaron Chapman, the rebound fell kindly to Idris El Mizouni who was quickest to react and slotted home.
The goal put a spring in Ipswich's step, and Jordan Roberts was a whisker away from making it 2-0 with a thumping free-kick from 30 yards
But on 32 minutes, Posh were level.
Ipswich foolishly gave teenager Jones too much time on the edge of the box, and he worked himself the space to send in a low shot that beat Przybek on his near post.
Posh ended the half with a flurry of attacks, but couldn't force their way into the lead.
At the start of the second half, Posh should have went ahead, but Ward sliced wide from eight yards after being put in on the left side of the penalty area by Dembele, who had worked he chance brilliantly.
Demeble was then just wide with a curling effort from 20 yards, and Posh were looking the more likely.
The Ivorian was proving to be a constant pest to the Ipswich defence, but he perhaps should have done better than lob the ball wide went sent clear by a long pass over the top from Mason.
Roberts shot straight at Chapman in a rare Ipswich attack, and as the game entered the closing stages Posh began to lose their attacking edge.
So much so, that on 83 minutes Ferguson turned to his big guns, bringing Toney and Eisa on for the excellent Jones and Kanu.
Before they touched the ball though, Chapman did well to tip an Emyr Huws free-kick over the top, before Toney almost scored a dramatic 90th-minute goal, his header saved by Przybek.
Despite Posh's dominance, Ipswich should have nicked it in the third minute of stoppage time, but Huws fired his low shot too close to Chapman, who got down well to his left to save.
With seconds remaining, nice interplay between Toney and Dembele created a chance for Tasdemir, but he slipped as he shot and his shot was blocked, setting up the penalty shootout.
Posh had the early advantage as Chapman saved from Brett McGavin, but then Dembele saw his effort saved.
It went to sudden death, and after Kent's penalty was saved, Ipswich's Barry Cotter held his nerve to win it.
Peterborough United: Chapman, Butler, Woodyard, Dembele, Bennett, Tasdemir, Ward (63m, Kent), Mason, Kanu (83m, Toney), Barker, Jones (83m, Eisa). Substitutes not used: O'Malley, Reed, Cartwright, Burrows.
Ipswich Town: Przybek, Cotter, Henderson, Skuse (46m, Smith), Kenlock, McGavin, Huws, Mizouni, Dobra, Roberts, Norwood. Substitutes not used: Alley, Hughes, Gibbs, Simpson, Georgiou, Folami
Goals: 23 mins: El Mizouni 0-1; 32 mins: Jones 1-1;
Bookings: Posh - Tasdemir, Butler; Ipswich - Smith, Huws, Roberts
Referee: Graham Salisbury