United's Under 18s recorded a solid win away at Birmingham City thanks to first half goals from Clark Greaves and Jake Kelly's deflected effort.
In a match heavily influenced by the windy conditions, it was United who made best of the situation but a goal for the hosts seven minutes from time made for a tense finale.
United were playing with the wind behind them in the first half and took full advantage of the conditions, creating several chances and ensuring Birmingham goalkeeper Josh Bradley-Hurst had to make several excellent saves to keep the score down.
It was Greaves who opened the scoring after 11 minutes when he hooked the ball home after Bradley-Hurst had pushed out Kelly's cross from the right.
Birmingham hit the post but that was as good as it got for the hosts during the opening 45 minutes, the conditions meaning Bradley-Hurst had to alert to push away Frank Maguire's corner.
Maguire also tested the keeper from long-range and then missed a great chance one on one but United's pressure told when Kelly fired home via a heavy deflection after the ball fell to him on the edge of the box from a corner.
It got even better for United when City striker Oumar Traore was shown a straight red card for an apparent headbutt on Tom Weaver with just half an hour of the match gone.
The second half was a much tighter affair as United defended heavily with the hosts now playing with the wind firmly behind them, but the centre-back duo of Weaver and Jean Belehouan stood tall to deny Birmingham any clear chances.
City did get a goal back with seven minutes to play through substitute Ramello Mitchell, the forward hammering home a low effort from a tight angle to ensure a nervy finale.
But despite throwing everything at United in the final exchanges, the Blades held on and could have extended their lead when substitute Zak Brunt rolled the ball agonisingly wide when through one-on-one with the goalkeeper.
Blades: S. Kelly, Williams, Foulstone, Neal, Weaver, Belehouan, J. Kelly, Maguire, Gaxha, Ompreon (Brunt 72), Greaves (Hackford 87).
Unused: Clarke, Chapman, Anderson.