Only when Manchester United rediscovered their old DNA, playing with width and passion, did they recover from pending humiliation here. Only when Ashley Young came on to give width down the left, and Antonio Valencia attacked down the right, did Louis van Gaal's side score respectively through Ander Herrera and Marouane Fellaini, setting up a quarter-final with Arsenal at Old Trafford.
Until Young's arrival on the hour, United were trailing to Scott Laird's strike, a goal that will not make enjoyable reviewing for David De Gea. The Premier League side were struggling to break down Preston's determined defence. Radamel Falcao was poor, and replaced by Young. Wayne Rooney and Angel Di Maria were failing to make an impact. Young suddenly gave them an outlet on the right, and delivery, bringing Herrera's goal which was etched with controversy as Rooney was distracting the Preston keeper, Thorsten Stuckmann.
Valencia then supplied the width on the right lifting a ball in for Fellaini, whose first effort was saved by Stuckmann but the Belgian rammed in the loose ball.
Rooney completed the comeback from the spot, although again the case for video technology was advanced as it was difficult to discern any contact when challenged by Stuckmann. There was no debating the penalty which Rooney thumped past Stuckmann. Whatever the controversy, the game certainly ended with United in charge and heading to that quarter-final with Arsenal. Preston can reflect on a prodigious performance, certainly for an hour, and returning to their promotion push.
Even before Laird struck early in the second half, forcing United to dig deep and rally impressively, Deepdale had been quivering with excitement. Deepdale had waited 43 years for this visit. The excitement had intensified before kick-off as the quarter-final draw was relayed over the huge screen above the United fans, granting the winners a home tie against Arsenal.
The visiting thousands in the Bill Shankly Kop took delight also in the sight of Rooney playing in his preferred position, up top with Falcao, with Fellaini in the hole. Rooney almost muscled his way through, running on to a pass from Di Maria, but ran into a wall of white shirts. Deepdale oozed defiance.
The place was packed to the rafters, the Preston fans singing "there's only one David Moyes" and then paying a loud, emotional tribute to their greatest son who passed away a year and two days ago.
"There's only one Sir Tom Finney" chorused the North End supporters at minute No 7.
The sides had first met in the Cup in 1890 when United were Newton Heath but this was their first encounter since 1972 when George Best, Bobby Charlton, Brian Kidd and Denis Law visited Deepdale. North End lost to two late Alan Gowling goals but did have the consolation of record gate receipts of pounds 20,022. With television money, this tie was worth around pounds 600,000 to Preston. For Simon Grayson's men, nobody could put a price on this opportunity to stare down United.
Their main focus is promotion from League One but their hunger was inescapable. Grayson's players were so quick to close down Van Gaal's.
John Welsh flew in strongly but fairly into a challenge on Di Maria, a League One stalwart introducing himself to a Champions League winner.
Supporters of Welsh's old club, Liverpool, would have particularly enjoyed that.
United were labouring to break through, thwarted by the resilience of Preston's defence. Bailey Wright fouled Falcao 25 yards out.
Rooney and Di Maria stood over the ball, the Englishman shaping to take the free-kick but it was the Argentinian's left foot that met the ball, curling it wide.
Preston were working overtime. Breaks from Falcao and Antonio Valencia were stopped by Paul Huntington. Kevin Davies was constantly dropping deep, helping out his midfield. Preston's No 9 even required a change of top, re-emerging with a shirt without a name or number. Not that United or the referee, Phil Dowd, needed any additional information as to the perpetrator of the first bookable offence, an upending of Herrera.
Davies accepted the booking, and got on with hassling the distinguished guests.
Preston fans were loving their team's commitment. Howls of laughter rolled down from the Alan Kelly Town End as Di Maria overhit a cross into their midst. There were some nervous moments before the huge applause at the break, not least when Rooney ran on to an inspired long pass from Di Maria but Stuckmann leapt from his line to intervene.
Wright, defending with strength and timing, then cleared as Rooney threatened. As the half closed, Davies went storming down the left, lifting in a ball that Paul Gallagher shot goalwards but it was easy for De Gea.
United's Spaniard has matured into one of the leading keepers in the world, a byword for secure hands yet he was caught out two minutes into the second period. When Davies fed Laird, the left wing-back let fly, the ball catching the tip of Valencia's boot and embarrassing De Gea. The keeper would have expected to have dealt with a shot still hurtling close to him but it powered its way through.
United were poor, lacking focus and dynamism. Di Maria took range from far out, leading to a simple save for Stuckmann, who then grasped the ball from under the feet of Fellaini. The disappointing Falcao was replaced by Ashley Young, who had an immediate impact, giving United more width. After 65 minutes, Young picked out Herrera, who drove his shot in off the post. Stuckmann was furious, rushing towards Dowd, arguing that Rooney was obstructing his vision which he clearly had been. The case for video technology was again enhanced.
Davies was then fortunate to stay on for another transgression, flattening Chris Smalling, and Dowd showing remarkable leniency. United poured their anger into gaining the lead and their width paid off. Valencia crossed from the right, and Fellaini scored at the second attempt.
Preston had a late chance when Callum Robinson's shot was held before Rooney made it 3-1 to United with three minutes remaining. Rooney playing up top and United playing with more width is surely the way ahead for Van Gaal now.