United's final home fixture of an impressive 2017/18 campaign ended in defeat, to end hopes of a play-off place.
Alan Browne scored the only goal of an even contest at Bramall Lane.
Boss Wilder made three changes for the encounter with Preston. Freeman returned to first-team action, with Clarke and skipper Sharp reunited in attack, with Baldock, Lundstram and Donaldson dropping to the bench.
The first really opportunity came the way of the visitors has Robinson got the better of Stearman, only to see his shot from inside the area blocked by Evans. In response, United latched onto a second ball and Clarke saw his goal bound effort blocked at the expense of a corner by Davies.
The first booking of the game, saw Fisher carded after catching Stevens. That was quickly followed, by Harrop seeing yellow for a late challenge on Basham. Back to the action, Clarke almost forced home the opener at the near post from Stevens low cross, only for Rudd to deny him from point-blank range.
As half-time approached, Fleck became the latest into the referee's notebook, following a miscommunication with O'Connell saw him foul Harrop. Fleck's next contribution nearly opened the scoring, but his shot was spectacularly headed over by Cunningham, before the North End skipper denied Freeman from the resulting corner.
United were quickly out of the blocks in the second-half, with Clarke testing Rudd from distance. At the other end, Basham had to be alert to sniff out the danger, as Robinson fired a ball across United's six-yard box.
The bookings continued to come, with Evans the latest to be added to Linnington's collection, for a late tackle on Cunningham. But in the 57th minute, the visitors went ahead. Blackman could only parry Harrop's shot and BROWNE reacted quickest to score on the rebound.
United reacted positively, Fisher cleared Basham's cross over his own crossbar, before Cunningham denied the Blades from a corner, with a last-ditched header at the back post, with Rudd beaten. Stevens was booked for a foul on Browne, before Brooks was introduced in place of Evans.
Preston thought they'd double their lead, when Clarke headed home, only for the assistant referee to flag for offside. Baldock replaced Freeman and Rudd was at his best twice in a matter of second, tipping over from Brooks, after punching clear Baldock's inviting cross.
Tempers threatened to boil over as United prepared to take an attacking free-kick, then Sharp was booked for watching Huntington go to ground again. With the clocking ticking down, Preston continued to block United shots at goal, with Duffy the latest to be denied.
Six minutes of added time were signalled and it was the visitors who were going forward, with Blackman tipping over a shot from Robinson. Despite United's best efforts, North End held on to end the Blades hopes of a top-six finish.
Blades: Blackman, Stevens, Fleck, O'Connell, Basham, Clarke, Sharp, Freeman (Baldock 76), Stearman (Leonard 80), L. Evans (Brooks 66), Duffy.
Unused: Moore, Lundstram, Donaldson, Lafferty.
Preston: Rudd, Cunningham, Pearson, Browne, Harrop (Gallagher 66), Johnson (Clarke 66), Fisher, Davies, Huntington, Maguire (Barkhuizen 58), Robinson.
Unused: Moult, Maxwell, Earl, Bodin.