Alan Browne netted his seventh Championship goal of the season
Alan Browne's second-half winner kept alive Preston North End's Championship play-off hopes, but ended those of Sheffield United.
Browne poked home the winner, pouncing when Blades goalkeeper Jamal Blackman parried Josh Harrop's shot.
United had the best chance of a cagey first half, Leon Clarke forcing a point-blank save from Declan Rudd.
The win brought Preston within two points of Derby County in the final play-off spot.
Both sides kicked off needing victory to maintain their play-off chances, as well as other results to go their way.
But clear openings were thin on the ground in the first half, with Clarke's effort the only attempt on target.
The game opened up after the break and, following Browne's goal, Preston substitute Tom Clarke touched Tom Barkhuizen's header into the net - but from an offside position.
United piled forward for an equaliser as David Brooks' shot was pushed over by Rudd, and Mark Duffy's effort deflected wide, but the visitors held on for only their second win at Bramall Lane in their last 19 visits.
The Lilywhites moved up two places to seventh, but will be leapfrogged by Millwall if they avoid defeat at Middlesbrough (17:30 BST), while the Blades stayed 11th.
Sheffield United boss Chris Wilder:
"We've come a very long way in a short space of time and for us to take it to the 45th game - I don't think anybody would've expected that.
"Ultimately we're disappointed today that we didn't finish off our home campaign which, I believe, has been very very positive.
"We've had some great results, and possibly more performances than results."
Preston North End manager Alex Neil:
"It's certainly one of those games where we'll take the result and the performance separately.
"It's probably as poor as we've played technically in terms of moving the ball and controlling the game, but we still managed to win the game.
"I don't want to take anything away from the players. They've dug in and done what they had to do to get the result, but it's certainly not a vintage performance from us."
