United's U23s fell to their first league defeat of the season as goals either side of half-time condemned a young side to a 2-1 defeat at home to Bristol City.
A header in first half stoppage time from Tom Richards followed by Joe Morrell's penalty soon after the break was enough for Bristol to walk away with the three points despite George Broadbent's consolation for Blades with the final kick of the match.
In a first half which gave up very few chances for either side, the visitors had the better of the ball and Marcus Dewhurst was called upon to push away a dangerous cross from Cameron Pring early on.
Despite the pressure, the best chances fell to United. Jordan Hallam curled over after a good break from George Cantrill before captain Jordan Doherty was somehow denied by a point-blank save from Sesay after a corner fell kindly for the centre-back.
But Bristol took the lead on the break as Holden got free down the left and saw his inch-perfect cross headed home from close range by Richards in what was the final action of the first half.
The second half frustratingly started in similar fashion for United. Jake Andrews' shot from outside the area was spilled by Dewhurst and the goalkeeper couldn't recover in time without bringing down Richards, giving Bristol the chance to double the lead from the spot.
City captain Morrell stepped up and sent Dewhurst the wrong way to double the lead but it didn't stop United doing their best to mount a comeback.
Hallam somehow saw a shot just deflected past the post for a corner after his effort had beaten Sesay before he was denied by a close range save from the goalkeeper shortly after.
Sesay was in top form but presented United with an opportunity soon after his heroics, spilling a cross which eventually led to Hallam slicing an effort wide from close range, much to the City keeper's relief.
United did get a deserved goal but it came too late to be anything more than a consolation. Bristol gave the ball away whilst passing around at the back and substitute George Broadbent calmly finished into the corner of the net.
Blades: Dewhurst, Gordon (Broadbent 77), Ferguson, Doherty, Cantrill, York, Sheppeard, Oure (Greaves 61), Mallon, Hallam, Boyes.
Unused: Kelly, Ompreon, Potts.