Diego De Girolamo netted a spectacular double but United's youngsters were forced to settle for a point after conceding two late goals.
With the U21s in action at Crewe on Monday, the Blades drafted in several U16s on to the bench, but looked set to claim a deserved win until Crewe threw caution to the wind in the final ten minutes.
Despite the obvious disappointment of losing a two-goal advantage against the Alex, United dominated for long periods and can take plenty of heart after extending the unbeaten start to the campaign.
After having plenty of the play in the opening half hour, United took the lead in eye-catching style in the 33rd minute, when DE GIROLAMO rifled home a wonderful volley after the visiting defence failed to clear a free-kick.
Owen Heather should have made it two on the stroke of half-time, but immediately after the break the home side doubled their lead when DE GIROLAMO lashed home an unstoppable effort from fully 30 yards.
The hosts were perhaps a little guilty of sitting back on their lead thereafter and unfortunately paid the price as the succumb to two late goals after Crewe started playing a more direct style, as the visitors undeservedly rescued a share of the spoils.
Blades: Lynch, Payling, Ptak, Whiteman, Scarisbrick, J. Williams, Khan, Dimaio, Smith, De Girolamo, Heather.
Unused: Eyre, Owen, Coustrain, Evans, Lewin.