United's youngsters slipped to a 2-1 against Derby County at Moor Farm on Wednesday afternoon.
Second-half goals from Kwame Thomas and Michael Hoganson put the Rams in charge of the game, before Dominic Calvert-Lewin netted a late consolation for the visitors.
After a goalless first period, County hit United with their first attack of the second period. After the Blades failed to clear their lines, THOMAS reacted quickest to force the ball home from close range.
With United chasing the game in the final ten minutes, Derby doubled their advantage, when HOGANSON cut inside from the right before lashing home past Willis.
The Blades responded immediately to half the deficit. CALVERT-LEWIN scored at the second attempt after Roos had parried his initial goalbound effort
Blades: Willis, Paling, Johns, Dimaio, Banton, McGinty, Khan (Reed 71), Whitehouse, De Girolamo (Whiteman 71), Calvert-Lewin, McFadzean (Smith 59).
Unused: Eastwood, Evans