Substitute Sharp converted what proved to be the winner in the 73rd minute after referee Andy Madley awarded a penalty for Federico Fernández’s handball following a lengthy VAR check.
The Magpies had been reduced to ten men on the stroke of half time when Ryan Fraser was dismissed after picking up a second yellow card.
And Steve Bruce’s side couldn’t find a way back into the contest as the Blades held on to take the points at Bramall Lane.
The Premier League’s bottom club came out searching for their first win of the campaign, and John Lundstram signalled their intent early on with a swerving shot which flew well wide.
But minutes later they went closer after a neat, flowing move. It resulted in Lundstram slipping a pass through for David McGoldrick, whose low strike was parried away by Karl Darlow, who was preferred to the fit-again Martin Dúbravka between the sticks.
Lundstram had another sight of goal, sending an effort over as Newcastle struggled to prise open the Blades’ backline. Their only real opportunity came before the half-hour, when Fernández hooked over a cross for leading goalscorer Callum Wilson, who headed just past Aaron Ramsdale’s post.
That was as good as it got for United in the first half, as their hosts set about breaking the deadlock. Ethan Ampadu’s inviting cross was nodded over the bar by the impressive McGoldrick, before a stunning, perfectly-timed sliding challenge from Fernández denied Oliver Burke as he surged forward and tried to get a shot away.
The pressure continued in the half’s closing stages, with a McGoldrick cutback looking destined to be turned home by Burke until Paul Dummett’s timely intervention. Jayden Bogle’s left-footed effort was then beaten away by Darlow but in the final moments of the first period, United were reduced to ten men. Fraser’s challenge on McGoldrick, not long after his first caution, was deemed worthy of a second yellow by referee Madley and Bruce’s side faced up to the second half a man light.
Bogle forced another save from Darlow after the restart as the Blades replaced defender Chris Basham with forward Rhian Brewster as they tried to make their numerical advantage count. Billy Sharp was then introduced from the bench, with Burke departing, and they continued to create: Bogle fired wide before another Lundstram strike was charged down.
The game’s pivotal moment came with just under 20 minutes remaining. Sharp chased a through ball alongside Fernández, who appeared to inadvertently handle the ball under pressure from the veteran frontman. After a protracted VAR check, which involved Madley heading over to view the incident on a monitor, a penalty was awarded and duly dispatched by Sharp, who sent Darlow the wrong way from the spot.
Bruce threw on Andy Carroll for the final quarter of an hour as the visitors tried to find a way back, with Wilson heading a Jeff Hendrick shot straight at Ramsdale just moments before Brewster’s deflected drive struck Darlow’s upright at the other end.
The Magpies committed bodies forward as the game drew to a close but couldn’t muster an equaliser against the side they beat twice last term. There was a late free kick from substitute Jacob Murphy, which Ramsdale held, and a late scare for the hosts when Bogle chested a long ball just wide of his own goal, but Chris Wilder’s side held on to claim the points.
