Simeon Oure's late strike earned United's Under 23s a point on the road after trailing Cardiff City for most of their encounter on Monday night.
It was looking like frustrating night all round as United created plenty of good chances, particularly in the first half, but failed to put the ball in the back of the net for the majority of the game.
The performance though couldn't be criticised as the Blades played some incisive, fast football in the opening 45 before being hit on the break in a rare chance for the hosts.
Harrison Neal saw an effort deflected into the arms of Alex Smithies in the opening minutes before Daniel Bramall saw several good opportunities come and go.
The first was an effort deflected away by the Cardiff defenders before the second came, but Bramall hesitated in front of goal and allowed a defender to get back.
Harry Boyes forced a good save out of Smithies with an effort from range but the best chance fell to Simeon Oure who headed a brilliant cross wide from close-range.
Less than a minute after Oure's miss, Cardiff scored when Rhys Healey held off his marker and fired low past Jordan Amissah.
The second half was a more frustrating affair as United struggled to create the chances they had in the first half but continued to go close as Jake Bennett and Harry Sheppeard both saw efforts from outside the box go close.
Jake Young was introduced with half an hour to go and he too fired an effort just over as United looked for a way back into a game they'd had much the better of.
And the goal came in the nick of time as the game approached its final five minutes. Young provided a superb cross-field ball for Boyes, the winger in turn setting up Oure who turned and fired home via a deflection to level the scores.
Blades: Amissah, Bennett (Gordon 70), Armstrong, Neal, Wright, York (Williams 76), Sheppeard, Bramall (Young 62), Oure, Greaves, Boyes.
Unused: S. Kelly, Belehouan.