United's Under 23s took the spoils in the South Yorkshire derby against Barnsley thanks to Jordan Hallam's brilliant effort in the first half.
During a closely fought contest at Stocksbridge which saw the visitors have the better of both possession and chances, United dug deep and fought hard in defence and also had goalkeeper Jordan Amissah to thank for his first half penalty save.
Barnsley started the game on the front foot and had the clearest chance to open the scoring when striker Gerry McDonagh volleyed over Louis Wardle's cross from close range.
But it was the Blades who took the lead just inside 20 minutes. Harry Sheppeard's cross from the right was headed only as far as Hallam, the United striker firing home a first-time half-volley from the edge of the box which crashed in off the underside of the bar.
Hallam's goal was largely as good as it got for United going forward as they came under pressure from a Barnsley side pressing for an equaliser.
Tricky winger Amir Berkovits was the main threat, first curling wide from inside the box when he'd done the hard work before a superb Reece York challenge denied him another clear sight on goal.
Barnsley had the best chance to equaliser just before the break when George Cantrill brought down McDonagh inside the area, the referee pointing to the penalty spot.
But Amissah guessed right and held onto Wardle's attempt from the spot to ensure United took the lead into the break.
Hallam flicked a nonchalant effort just wide as Barnsley continued to apply pressure after the break. Chisholm should have levelled after a cross from Walsh evaded him, but United defender Kyron Gordon may have got a crucial touch to put him off.
Chisholm was the main threat after the break, forcing Amissah into another save before dragging an effort wide when he should have done better.
Amissah continued to star, saving from Walsh at his near post before Simeon Oure missed a big chance late on to wrap things up, not connecting properly with his effort after good work from Hallam.
But it didn't come back to bite the Blades who held on to record the win and take the points on derby day.
Blades: Amissah, Gordon, Mallon, Broadbent, Cantrill, York, Sheppeard, O. Greaves, Oure, Hallam, Boyes (Williams 53).
Unused: Weaver, S. Kelly, Neal, Ackroyd.