United's Under 18s were denied the perfect start to 2019 when Kareem Hassan Smith's 96th minute equaliser cancelled out Reon Potts' goal two minutes earlier which had looked to be the dramatic late winner the Blades had been searching for.
It was an entertaining and frantic encounter throughout, but United will look back and think they could have been well clear at the break after dominating the opening half of the match.
United were on top from the off without creating major chances. Leo Gaxha saw an effort blocked before firing over from a tight angle but the Blades waited no longer than 20 minutes to make their fast start count.
A corner from the left from George Broadbent found the head of Sammy Ompreon, the forward flicking a header into the far corner of the net to get the year off to the perfect start.
But United didn't capitalise on their momentum and dominance. Zak Brunt saw a powerful effort pushed over by Edward Onaluwm before Ompreon went close right on half-time, his volley deflected inches wide of the goal.
After the break the game turned in Barnsley's favour as United struggle to maintain their fast pace after half-time.
Frankie Maguire wasted a good chance to double the lead after more good work from Ompreon but the hosts turned the screw, forcing Jordan Amissah into a brilliant double save to deny both Kyle Connell and Aiden Marsh in quick succession.
Just minutes later though and Marsh did find the net, firing home a low effort from the edge of the box into the far corner of the net.
With 20 minutes to go though United were given the perfect chance to retake the lead when a defender was penalised for handball inside the box. Brunt stepped up but his powerful effort was pushed away by Onaluwm,
Reon Potts and Jack Stainrod were introduced as United looked for a late winner and deep into stoppage time it looked like Potts had got it.
A free-kick into the box was headed on and Potts managed to steer it home almost on the line to spark wild celebrations among the United players.
But there was more drama to come as United then didn't deal with a free-kick of Barnsley's own, leading to Smith to hammer an effort which Amissah pushed away, only for it to fall back to Smith who made no mistake with the second attempt.
It proved to be the final action of an exciting but in the end frustrating match for United.
Blades: Amissah, Williams, Boyes, Neal, Gordon, Belehouan, Maguire, Broadbent, Gaxha (Potts 74), Brunt, Ompreon (Stainrod 86).
Unused subs: Chapman, Anderson, Weaver.