United's Under 18s played out a second 0-0 in a row after playing the whole second half against Barnsley with 10 men.
Despite George Broadbent's red card in the opening minutes of the second half, United had the best chances and improved when Jake Young was introduced at half-time but once again lacked the killer instinct in front of goal.
The first half was a very quiet affair and in reality neither side was able to create a clear cut chance during the opening 45 minutes as both defences cancelled each other out.
The action started early in the second half when Broadbent received a straight red card just 90 seconds after the break for what looked like a kick at an opponent.
But United were livelier for the half-time introduction of Jake Young, the striker going close first on the hour mark when he scooped a lobbed effort onto the top of the crossbar.
Young was a constant threat and forced a good save out of the Barnsley goalkeeper soon after as United pressed for a winner.
The game became more and more stretched in the dying minutes and Barnsley very nearly stole it when a header from a corner came back off the crossbar.
There was also one last chance for United deep into stoppage time when Young was once again denied and a sliding tackle denied Andre Brooks a tap-in.
Blades: S. Kelly, Williams, Gomis, Maguire (J. Kelly 88), Hall, Belehouan, Stainrod (Young 46), Broadbent, Ackroyd (Gaxha 46), Brunt, Brooks.
Unused: Amissah, Ompreon.