Dele Alli struck in the final three minutes as the Dons picked up an impressive victory at Bramall Lane and extended their unbeaten run in the league to nine games.
Alli tapped home Danny Green’s deflected free-kick to move the men from MK1 to within just two points of top spot with a game in hand.
Will Grigg, who replaced Benik Afobe in the only change for the Dons as fourth and fifth went head-to-head in South Yorkshire, saw an early effort deflect behind from the edge of the box as the men from MK1 settled well.
Karl Robinson’s side continued to dominate possession and territorial advantage as the clock ticked past the 10-minute mark, and Dele Alli was the next to threaten but he was denied by Jay McEveley as he looked set to shoot.
Jordan Spence and Carl Baker were linking up well down the right-hand side and the latter had a shot blocked after the pair combined while, at the other end, David Martin comfortably gathered Chris Basham’s 20-yard curling effort before Stefan Scougall fired wide from a similar distance 18 minutes in.
Those chances lifted the Blades, who went very close to opening the scoring three minutes later but Basham couldn’t quite connect with Bob Harris’ dangerous left-wing cross.
The Dons stemmed the tide as a good ebb and flow to the fixture ensued for the next 15 minutes, although both sides found it difficult to create any clear-cut chances during that period.
Jamal Campbell-Ryce registered the next shot on target with 10 minutes remaining of the first half, stinging the palms of Martin from a tight angle inside the Dons’ box.
That was the last chance of an evenly-contested opening 45, while the first opportunity of the second half saw Scougall scuff Campbell-Ryce’s cross when well placed on 48 minutes.
Scougall did better two minutes later when he forced Martin into a save from 22 yards as Nigel Clough’s men started on the front-foot.
Afobe was introduced for Reeves on 54 minutes as Robinson aimed to inject some spark into the Dons attack, with the Arsenal loanee going up top and Grigg dropping back into the No.10 role.
The 18-goal man’s first real foray forward on 61 minutes caused problems for the Blades defence as he out-paced Ryan Flynn and helped win a corner – Antony Kay saw his header from the resulting set-piece cleared off the line by Jamie Murphy.
The hosts responded with a shot from Murphy which was easily gathered by Martin midway through the second half, before Danny Green replaced Daniel Powell and took up the right-wing position with Baker moving to the left.
Paddy McCarthy had the ball in the back of the Dons net on 76 minutes but the goal was ruled out for offside after Marc McNulty’s initial header had come back off the post from a free-kick.
The Dons took full advantage of a good set-piece opportunity on 87 minutes when, after former trialist McEveley had brought down Kay 20 yards out, Alli tapped home at the back post from Green’s deflected free-kick, sending the noisy travelling supporters behind that goal into delirium.
They then withheld a late charge from the hosts to seal an impressive three points and secure their 11th clean sheet of the season.
Starting XI: Martin; Spence, Kay, McFadzean, Hodson; Potter (c), Alli; Baker, Reeves (Afobe 54), Powell (Green 69); Grigg (Flanagan 90+1).
Unused subs: McLoughlin, Baldock, Bowditch.
Goals: Alli (87).
Booked: Hodson, Alli, McFadzean, Kay, Green, Afobe.
Attendance: 17, 030 (268 Dons fans)