Jaroslaw Fojut’s stoppage-time winner handed Dundee United a League Cup quarter-final slot as their 1-0 win at Tannadice extended the Arabs’ unbeaten run against city rivals Dundee to a decade.
The Dark Blues had played for more than an hour with 10 men but failed to cling on as the Polish centre-half powered home his dramatic header.
Jackie McNamara’s team had eased past the Dark Blues with a four-goal Scottish Premiership thrashing on Sunday.
But Sunday’s romp did not stop the United boss ringing the changes as Gary Mackay-Steven, Chris Erskine and Mario Bilate made way for Nadir Ciftci – back from suspension – Stuart Armstrong and Blair Spittal.
Dee boss Paul Hartley, meanwhile, attempted to shore up his side team after suffering defeat for the first time this season. The enigmatic Gary Harkins and Philip Roberts paid the price as Luka Tankulic and Martin Boyle started.
But it was the visitors who grabbed the game by the scruff of the neck in the early stages.
They wasted their big chance to grab a first derby victory since November 2004, however, when Greg Stewart saw his eighth-minute penalty by turned away by United keeper Radoslaw Cierzniak’s improvised stop.
And their hopes were dented further when Martin Boyle was dismissed for his last-man tug on Stuart Armstrong just before the half-hour mark.
United struck the woodwork three times but kept their composure after setting up camp in the visitors’ half for most of the second period.
And they got their reward with just seconds remaining as Fojut’s goal sent the Tangerine section of the 14,000 sell-out into raptures.