United's U23s ended their campaign with an unfortunate home defeat to Birmingham City on Wednesday afternoon.
Two late Kyle McFarlane goals won it for the Blues, as United ended in fourth place in the Professional Development League.
City had the first opportunity of the game as a corner swung in by Stirk was met by Lupano but his header was well saved by trialist goalkeeper Greaves.
United came close as Mallon drove down the left and fired a ball across goal that was destined for Smith to tap in before Redmond cut it out.
The deadlock was almost broke on 42 minutes as Gilmour's right sided corner curled over everyone and bounced off of the post.
As the half drew to an end the Blades had another opportunity to take the lead when Mallon cut back for Smith seven yards out but the forward could only fire just over, despite a promising position.
On 58 minutes, Amartey picked up the ball on the halfway line for City and drove all the way to the area only to see his curling effort ricochet off the post.
The visitors continued to prove to be a threat on the counter attack as McFarlane went close twice in the space of 10 minutes with a block from Graham and a Greaves save denying him respectively.
The opening goal arrived on 80 minutes as substitute Concannon slipped Bernard in behind who squared for MCFARLANE to complete the move by finishing into an empty net to put the Blues ahead.
Birmingham would have the game wrapped up with four minutes left on the clock as the same duo combined. Bernard crossed for MCFARLANE to poke home from close range to condemn the Blades to defeat.
Blades: Greaves, Ferguson, Norrington-Davies (Elstone 62), Graham, Cantrill, Semple, Gilmour, Slater, Smith, Doherty, Mallon (Oure 52).
Unused: Broadbent, Weaver, Potts.