United twice came from behind to earn a point against Watford at Vicarage Road in the Professional Development League.
Former Manchester United striker Federico Macheda, on trial with the Hornets, gave the home side a half-time lead but Jordan Hallam levelled, poking home after Jake Wright had headed across goal from the back post.
Michael Folivi restored Watford's lead but skipper Callum Semple netted a 70th minute equaliser with a well-placed header from a set-piece to earn United a point, which they thoroughly deserved in the opinion of Coach John Dungworth.
Dungworth commented: "We felt we were the better side first-half, but found ourselves behind because of a defensive misunderstanding.
"But the lads reacted positively and Jordy (Hallam) applied the final touch to Jake's header and it was very much game on.
"Unfortunately, Watford's experience and quality got them back in front, but credit to the players, they stuck in there, showed good character and in the end we were good value for a draw against Premier League opposition."
Blades: Long, Charlesworth, Kelly, Wallace (Gilmour 12), Cummings, Semple, Slater (Graham 89), Whiteman, Wright, Hallam, K Smith.
Unused: Pollard, Burton, T Smith.