United's U18s slipped to a narrow loss at Birmingham City at the weekend, despite a goal from substitute Spencer Maw.
A late goal proved decisive in the Midlands, despite a rotated United side creating numerous opportunities of their own.
The first-half was largely an open affair with both sides having chances to open the scoring.
United had two early corners in quick succession but Hall and then Semple fired over when well positioned in the penalty area.
At the other end, Birmingham got in behind the Blades defence and beat Perryman, only for Cummings to produce a last-gasp clearance.
Before the interval the Bladed could have taken the lead through Hallam and Hall and those missed opportunities would ultimately prove costly.
The deadlock was broken in the 50th minute as a breakdown in communications between Semple and Perryman allowed the Blues striker to latch onto the loose ball and fire home.
But in the 68th minute United responded in the best possible manner, MAW broke inside and fired into the bottom corner with a left-footed strike.
In the remaining minutes both sides had chances to win the game, but it was the hosts who stole all three points from a looping set-piece that landed at the feet of Blues player who fired home from close-range.
Blades: Perryman, Charlesworth, Cantrill, Semple, Cummings, Ford (Litchfield 67), Mallon, Gilmour, Portman (Maw 57), Hallam, Hall (Burton 81).
Unused: Adebowale, Warhurst.