An exceptionally disciplined display helped the Blades secure a place in the third round of the FA Cup with Budweiser and avoid the potential banana skin at Cambridge United.
In front of the BT Sport cameras, Nigel Clough's side inflicted Cambridge's first home defeat of the season - they had previously won all ten of their Conference games at the R Costings Abbey Stadium.
Jose Baxter netted in the first half and substitute Jamie Murphy added the second after the break.
Boss Clough was forced into two changes with McMahon suspended and White not available under terms of his loan from Leeds. Flynn and Lappin returned to the starting line-up, whilst Brandy was back on the bench and joined by U21s captain, Kennedy.
The first surprise of the day saw United begin with a 3-5-2 formation. Maguire, Collins and Hill were the defensive unit with support from Flynn and Lappin in wing-back roles.
Goalmouth action at both ends inside the first five minutes set an encouraging tone. From the home side's first corner, Berry hammered the ball at Collins but penalty appeals were ignored, whilst for the Blades, Baxter met Coady's cross but Maxwell saved on his own goal-line.
The Cambridge goalkeeper, though, could do little to stop United's next attack, which brought the lead on 12 minutes. Flynn was afforded the space to put in a cross from the right, which looked behind a row of bodies, but BAXTER took up a neat position and blasted, on the turn, before Maxwell could react.
Cambridge hit straight back and within a minute they will feel they should have levelled. Dunk ran at the Blades defence and found Cunnington in space but Long rushed from his line to cut down the angle, making a fine block with his body.
Long then saved twice from Berry, the first a shot following a long throw and then a header from Tait's cross, whilst a change was needed midway through the first half when McGinn limped off, replaced by Murphy.
A good burst by Murphy, operating as a left wing-back, resulted in Lappin, now in a central midfield role, having a shot blocked and for the home side, Taylor smashed over after a fortunate bounce won him a shooting chance.
In the final 15 minutes of the first period the amount of opportunities in front of goal dried up but Cambridge can argue that they had the better of the possession and late on Long was the busier of the goalkeepers in terms of organisation and clearing any dangerous situations.
Cambridge started the second half well and their second and third penalty appeals of the game were waved away by referee Langford - Lappin and Maguire cut out crosses from Hughes and Dunk respectively with the home contingent asking for handball.
Unmarked Berry held his head in his hands after heading Dunk's corner wide whilst the Blades had a good chance to extend the lead on 52 minutes but Porter's header from Lappin's cross was too close to Maxwell.
United's second goal was not far away, though. On 58 minutes, Maguire's diagonal ball was helped on by Lappin and MURPHY cut inside from the left before lashing into the bottom corner of Maxwell's goal from the edge of the box.
The goal stunted Cambridge's enthusiasm for a while and United's professionalism, in terms of keeping possession and operating high up the pitch, frustrated the home side, although Hill needed to accept a booking to get himself out of trouble following a tangle with Dunk with 15 minutes remaining.
A Flynn shot was blocked and Baxter fired over the rebound, whilst Cambridge's fourth handball shout was against Lappin - again the referee was unmoved.
Just into the final ten minutes, a shot from Doyle was saved by Maxwell, whilst the hard-working Porter was replaced by Taylor late on.
As full-time approached Berry fired wide after a slack pass by Baxter but three minutes of added time elapsed without further problem as the Blades deservedly took up a place in the third round draw.
Cambridge: Maxwell, G. Taylor, Coulson, I. Miller, Champion, Cunnington (Roberts 60), Dunk (Arnold 82), Tait, Hughes, Berry, Appiah.
Unused: Bonner, Austin, Sam-Yorke, Spillane, Brown.
Blades: Long, Maguire. Hill, Flynn, Doyle, Porter (L. Taylor 86), Baxter, McGinn (Murphy 22), Collins, Coady, Lappin.
Unused: Howard, S. Miller, Cuvelier, Brandy, Kennedy.