Erik Tonne's second half goal protected United's unbeaten pre-season campaign.
A youthful side, led by Chris Morgan, recorded victory at Matlock on Wednesday evening to ensure the Blades won five and drew two of the warm-up matches in preparation for the new season.
Despite an energetic start from both sides, the only chance of the first 20 minutes came following an enterprising run from McFadzean, who beat three defenders but could not poke past the home goalkeeper.
For the Northern Premier League side, Joynes failed to get enough of a connection on his header from a Hindley cross and Grayson's half-volley was comfortable for Long. The best chance of the half also fell to Grayson, on 42 minutes, when he got the better of Salt but his close-range shot, after cutting in from the right, was saved by Long.
United came out with more vigour after the interval and were rewarded when the first opportunity resulted in a goal on 54 minutes. A patient build up involving Philliskirk and McAllister saw TONNE pick up possession 25 yards out and he held off the attention of Foster before firing into the bottom corner.
Philliskirk then forced a save out of goalkeeper Kennedy as United looked to extend the advantage.
Long was then called into action on a couple of occasions, making a comfortable save from Algar's chip and catching a McMahon shot, which was straight at him. However, the young goalkeeper's best effort was diving to his left and tipping over another Algar attempt on 80 minutes.
Algar's third attempt on goal late on was just wide as the Blades held on to protect a narrow but deserved victory.
Matlock: Kennedy, Harcourt, Roe, Foster, Yates, Featherstone (Lukic 58), Hindley (Algar 45), Davies (Ashmore 58), Joynes (Leesley 58), McMahon, Grayson (Ellington 45).
Unused: Bowler, Witcombe, Dennis, Travis.
Blades: Long, Hodder, T. Williams, Harriott, Salt, Foster, Tonne, McAllister, Ironside, Philliskirk, McFadzean (Pemberton 24).