Preston succumbed to a narrow defeat at Bramall Lane despite a determined effort against the promotion possibles.
An Ugo Ehiogu strike five minutes after the break separated two sides who looked good bets to be at the right end of the table come May - it just needs the right bounce of a ball or a deflection at the right time to re-ignite PNE's attacking aspirations.
It's now six defeats in seven for Alan Irvine's unfortunate men, who deserved more at a ground that has been a North End graveyard for the past 30 years.
As if Bramall Lane wasn't a difficult enough place for the unchanged North End side to visit, their task seemed to be made even harder just 75 seconds in as Sean St. Ledger took a blow to his right leg and was hurried to the sidelines for treatment.
It meant the remaining ten men were forced to defend a man light with Billy Jones dropping into the centre and Chris Sedgwick slotting is as a makeshift right back.
Fortunately, North End only had one threat to defend - a tame free kick from Brian Howard - and when returned to their full compliment with the return of a strapped up St. Ledger, PNE raced forward to take their first strike at goal through Sedgwick, Kenny smothering at his near post.
A more threatening moment arose as Andy Lonergan lept with great athleticism to come and make a claim for Naysmith's deep free kick, but with a crowd of bodies below him, they acted as a trip wire, leaving him without the ball and needing Jones to block Beattie's shot as it fell kindly for the striker on the edge of the six yard box.
The Lilywhites gave a good account of themselves throughout the opening stages, breaking well once they had soaked up the obligatory pressure from the home side.
McKenna's vision sent Sedgwick away to lead a three-on-two break, but that chance sadly couldn't be taken as his eventual cross landed just inches behind Stephen Elliott's run, while on a later foray forward, Parkin struck a low drive with some venom from 20 yards, requiring Kenny to collect his own parry as Elliott looked most likely to beat his marker in the race to the loose ball.
North End dominated large chunks of the game, somewhat surprising the hosts with their willingness to attack for much of the half.
Jon Parkin saw a shot blocked by Beattie as Billy Jones scampered into a crossing position to provide him within the box, and then Ehiogu's foul on the same striker led to a Ross Wallace free-kick, which was only kept out courtesy of a deflection off the wall which took it just wide.
The resulting corner was cleared at the first attempt as Mawene looked to head home from Nicholson's delivery, but the Scottish playmaker got the ball back and felt Matthew Spring had handled his second delivery into the box, leading to a loud appeal from the men in yellow as they went in search of a penalty that wasn't forthcoming from referee Whitestone.
Inevitably, the frenzied pace slowed as the half developed, which seemed more to the home side's advantage as it took some of the pressure away from their over worked defence. However, their impressive-looking breaks often came to nothing, with Lonergan blocking a number of well driven low shots from Webber and his striking colleagues.
Half time parity was a reasonable assessment of the game's pattern, but sadly that wasn't to last.
Within five minutes of the re-start, St. Ledger, who was battling on despite his leg being heavily strapped, was pulled up for handball on the edge of the box, and Quinn's subsequent curling free-kick, destined for the bottom corner, caused problems.
Lonergan did well to palm the ball away from danger, but waiting to pounce on the rebound was Webber. He squared to Ehiogu, and though the advanced centre half saw one shot blocked by his opposite number Mawene, the loose ball fell kindly for him to poke it home off the underside of the bar from eight yards.
The goal gave great hope to the home team, who seemed lifted as a group by the lead. Webber epitomised the new found belief by testing Lonergan from a wide angle having skipped through the challenges of Wallace and McEveley through quality footwork.
PNE needed to try something different to regain a foothold in the game, so boss Alan Irvine responded by giving Sheffield-born Neil Mellor the chance to prove himself in his home city for half an hour, replacing Elliott who had largely been given little to work with throughout in spite of Preston's promising forays.
A response in kind came from Wallace, who flashed a shot wide of the Kop End goal when looking for a netbuster after showing Ehiogu a clean pair of heels.
The game lost flow as a result of the increasing number of changes, with the opportunities at both ends nothing more than half chances.
Simon Whaley and Billy Sharp both arrived with just a few minutes remaining, in the hope of providing the tonic their respective sides needed, and it was nearly the latter that sealed the game on the break.
Barry Nicholson gave the ball an almighty thump from 25 yards as he looked to find a stoppage time leveller, but the rebound from Kenny's save landed just the wrong side of Mellor who waited to pounce, and that was the end of the road for North End.
PNE: Lonergan, Jones, Mawene, St. Ledger, McEveley, Sedgwick (sub Whaley 87), Nicholson, McKenna (capt), Wallace, Parkin, Elliott (sub Mellor 60). Subs: Chris Neal, Nolan, Jarrett.
Blades: Kenny, Naysmith (sub Jihai 46), Morgan (capt), Stokes, Beattie (sub Sharp 87), Webber (sub Halford 79), Howard, Spring, Quinn, Naughton, Ehiogu. Subs: Cotterill, Montgomery.
Attendance: 24,445
