Iliman Ndiaye looked to have rescued a point for the Blades on the stroke of 90 minutes, and when the fourth official added on five minutes there was hope inside Bramall Lane that they could go on to nick a winner.
But Reading, who had led since the first half thanks to a comprehensive finish from former Owl Lucas Joao, had other ideas and instead went up the other end and scored a winner, defender Tom McIntyre left all alone to poke home after the ball was knocked down into his path.
The defeat sees United miss the chance to further establish themselves in the play-off places, and they can count themselves fortunate that Middlesbrough only managed to draw with Bournemouth and Blackburn were beaten away at Peterborough.
Here’s how our man rated the Blades players ahead of Monday’s now even more pivotal clash away at Bristol City.
9. Ben Osborn 4
Replaced Sander Berge from the start and ended up at right wing-back after half-time. No shortage of industry as ever but perhaps missing a touch of invention when it was required against such stubborn opposition. Photo: Simon Bellis
10. Morgan Gibbs-White 4
Was perhaps fortunate to only escape with a booking after catching Ejaria high in the chest as he contested a bouncing ball with foot rather than head. Endured a frustrating afternoon after that, with nothing really coming off for him Photo: Simon Bellis
11. Oli McBurnie 3
Took a whack in a tackle in the first half and didn't move too freely after that, being replaced early in the second by Jebbison Photo: Simon Bellis
12. Subs: Sander Berge 5
Rested from the start, he had to come on at the break and gave United another attacking threat Photo: Darren Staples