United's U23s slipped to a narrow defeat at Loftus Road on Monday afternoon.
Goals from Bright Osayi-Samuel and Aramide Oteh either side of a Regan Slater strike were enough for QPR in the capital.
United created the first chance after being the better side in the opening stages as Slater slipped in Smith but his shot from a tight angle was parried and subsequently cleared.
But on 23 minutes the hosts would take the lead against the run of play as OSAYI-SAMUEL worked his way into the box and curled into the far corner leaving Eastwood with no chance.
The Blades restored parity in the 35th minute, when Smith played in SLATER down the right who skilfully cut back into the box and drilled home with his left foot to level proceedings.
Shortly afterwards United came close to taking the lead as a loose ball in the QPR area saw Gilmour win a tackle, but Oure's effort didn't have enough conviction to trouble Ingram.
Just before the half-time whistle, Eastwood would be called into action to deny Phillips with an excellent reflex save from Tilt's corner.
Prior to the hour, the Hoops would retake the lead as Cousins' initial effort was blocked and the ball ricocheted to OTEH who fired home at the near post.
On 65 minutes United had a golden chance to level as Potts had a shot saved into the path of trialist York, who scuffed his effort and it was cleared off the line by former Blades loanee Baptiste.
United kept up the pressure as the end of the game approached with Smith turning smartly away from Baptiste but couldn't beat Ingram in the QPR goal.
In injury time United came even close to levelling the scores for a second time, but Smith's well struck effort from the edge of the area was well saved by Ingram as the hosts held on.
Blades: Eastwood, Sheppeard, Boyes (Portman 58), York, Graham, Semple, Gilmour, Slater, Smith, Oure (Potts 61), Broadbent (Williams 76).