United's Under 18s recorded a well-deserved win and a third consecutive clean sheet in difficult conditions at Charlton Athletic.
Zak Brunt's fourth minute effort was all that separated the teams in the end but the Blades had plenty of chances to put the game to bed.
But it was Brunt's early strike, curling home from the edge of the box, that did the trick in a first half dominated by the windy conditions which made it difficult for both teams to create chances.
When the wind died down after the break it was the Blades who took the initiative and created several big chances to add to their lead.
Sam Ackroyd hit the bar with an effort from the angle before Drew Matthews joined him in hitting the woodwork just 60 seconds later.
Brunt and Tommy Williams were both denied by good saves from the Charlton goalkeeper as United struggled to wrap the game up.
And in the final seconds they were nearly made to pay but Sam Kelly pulled off an excellent save to claw away a late effort from range.
Blades: S.Kelly, Weaver, Brooks (Ompreon 40), Williams, Gordon, Gomis, J. Kelly, Matthews (Potts 74), Ackroyd, Brunt, Gaxha (Stainrod 86).
Unused: Chapman, Anderson.