A fantastic away performance saw Chesterfield advance to the third round of the FA Cup with a 1-0 win over high-flying League 1 side MK Dons at Stadium MK.Armand Gnanduillet proved to be the Chesterfield Cup hero, heading home Sam Clucas's cross eight minutes after half-time to give the Spireites the win their strong travelling backing craved.
The Spireites started with an attacking 4-4-2 formation, with Gnanduillet and Eoin Doyle leading the line and Clucas dropping back to an unfamilier left-back position in place of the suspended Dan Jones.
It was Gnanduillet who had the game's first golden opportunity when O'Shea's lofted ball found the striker in space and bearing down on goal, though he hesitated and gave a defender the time to catch up and concede a corner. From the set piece, Charlie Raglan was able to head but his effort lacked power and was saved by keeper David Martin.
The first 15 minutes belonged to the away side, Roberts broke into the left side of the box, eyes only for goal, and hit the side netting from an ever-less favourable angle.
The Dons showed their menace soon after, however, when Afobe forced Tommy Lee into a great low sprawling save. The ball fell to Dele Alli, who had a free shot, but the midfielder fired over.
MK were coming back into things and only a perfect sliding interception from Georg Margreitter prevented Alli from running clear through.
The game ebbing from one end to the other, Gnanduillet found space in the Dons' box, elected to cut the ball back and in doing so a home defender put the pink FA Cup ball into the side netting, with the keeper beaten.
Tendayi Darikwa was next to go close for the visitors, as he broke into the box, a clearance rebounded off him favourably and he lifted a measured lob that landed on the roof of the Dons' net.
The first half ended with both sides fancying a late opener, but goal less at the break both teams would have had cause for optimism in the second half.
No changes at the break, and the Spireites continued to look for an opener, O'Shea firing over a left-footed effort from 20 yards.
The break did come on 53 minutes, and it was the Spireites who put their noses in front. Clucas, forever a menace down the left, crossed for Gnanduillet, the big striker perfectly placed to nod home from six yards, sending the Spireites behind the goal into ecstacy.
Doyle thought he'd poked home a second four minutes later when Roberts' centre was converted, but as the Irishman wheeled away the assistant's flag was raised, off-side signalled.
The Spireites still pushing, Clucas then stung the keeper's palms with a rasping effort from the apex of the Dons' box.
Far from beaten, substitute Giorgio Rasulo curled an effort a yard wide from 20 yards, the Spireites not getting close enough to the Dons man.
Morsy hammered a shot that was punched away by the keeper as the clock ticked into added time, and an MK Dons corner was then hacked off the line as the Spireites hung onto their lead late on.
The fourth official signalled for four minutes of added time and the Spireiites withstood late pressure to go into the hat for the third round after a fine away victory at a strong MK side.
MK Dons: Martin (gk) - Lewington (c), McFadzean (Flanagan 77'), Kay, Potter, Grigg (Baldock 71'), Spence (Rasulo 71'), Baker, Alli, Powell, Afobe
Subs not used: McLoughlin (gk), Hodson, Tilney, Tshimanga
Chesterfield: Lee (gk) - Clucas, Raglan, Margreitter, Darikwa - Roberts (Hird 87'), Ryan, Morsy (c), O'Shea (Boco 65') - Doyle, Gnanduillet (Humphreys 80')
Subs not used: Wright (gk), Gardner, Evatt, Ariyibi
Chesterfield: Gnanduillet 53'
Attendance: 5,591 (1,125 away fans)