Despite dominating the second-half, the Blades exited the FA Youth Cup at the third-round stage on Wednesday night.
On a freezing night at Deepdale, Melle Muelensteen's early spot-kick proved to be the difference, with United having a late Jordan Hallam goal harshly chalked off for offside.
United made the worst possible start on a cold night in Lancashire, falling behind in the fifth minute. A long ball over the top wasn't dealt with by Charlesworth and O'Neil nipped in before Perryman, with the goalkeeper's momentum taking him into the North End midfielder. From the spot MEULENSTEEN fired home, straight down the middle of the goal.
In response, the Blades had a couple of corners, before Hallam forced a save from Roberts in the home goal after good work by Smith. In United's next attack, Hallam's right-wing cross was only cleared as far as Smith, but Roberts was equal to the winger's left-footed effort.
United were having the slightly better of the contest despite the scoreline, but just after the half hour from a swift counter attack by the home side saw Earl burst clear of Mallon down the left before squaring to Muelensteen who stung the palms of Perryman from the edge of the penalty area. Despite the best efforts of the visitors, North End held firm until the interval.
The Blades were quickly out of the blocks in the second-half, with skipper Slater and Hallam driving the team forward and in the 52nd minute United should have levelled proceedings. Mallon engineered a cross from the left and Smith was unmarked at the back post, but Roberts somehow kept out his effort with his legs.
The pressure was mounting on the North End goal, Slater fired in a shot from distance which Roberts saved diving away to his right, before Mallon fired over on the angle. In a search for that elusive equaliser, Cummings replaced Cantrill, with Parkhouse taking the place of Burton. Following a foul on Muelensteen, Gilmour became the night's first booking.
With 15 minutes remaining, O'Neil could have seen red for an elbow on Gilmour and moments later the pair clashed again, with the North End midfielder appearing to haul down United's number four off the ball. With the clocking ticking down, referee Lamb waved away appeals for a United penalty as Day seemed to catch Hallam.
The Blades had the best chance of the evening in the 86th minute. A long ball forward was flicked on by Parkhouse and Cummings, who had moments early being sent up front, raced clear only to be denied by Roberts. The offside flag then denied the Blades as Hallam fired home from another Parkhouse flick on from Gilmour's long throw.
Five minutes of stoppage time were indicated and United continued to throw everything forward, but ultimately all the efforts were in vain as North End held on to advance to round four.
Blades: Perryman, Charlesworth, Cantrill (Cummings 56), Gilmour, Graham, Semple, T. Smith, Slater, Burton (Parkhouse 67), Hallam, Mallon (Greaves 73),
Unused: Warhurst, Ford.