United's preparations took a small setback as they narrowly lost at Glanford Park on Saturday afternoon, despite mounting a second half comeback.
Scunthorpe took their chances in the opening 45 minutes, with Colin Daniel netting a brace, either side of a goal from Alfie Beestin. But the Blades were much improved after the interval but fell just short of levelling the game, despite efforts from substitutes Rhian Brewster and Iliman Ndiaye.
Boss Heckingbottom rotated his squad again for Saturday's clash with the Iron, with youngsters Amissah and Arblaster given a chance to impress from the start, with United's most recent addition Clark named on the bench.
United were quickly out of the block as Lowe volleyed over at the back post from an excellent deep cross from Broadbent, but after both teams had enjoyed spells of possession, it was Scunthorpe who had a couple of forays into the Blades area, before Feeney latched on to a long ball forward and tested Amissah.
On 21 minutes, a slip from Broadbent as he attempted to clear Nuttall's cross allowed DANIEL time to control before rifling past Amissah. United's response would have been instant, but Blades loanee Dewhurst was at his best to deny Robinson at the back post from Fleck's inswinging corner.
Moments after the half hour, things went from bad to much worse for the visitors. Scunthorpe doubled their led on 33 minutes as BEESTIN applied the finishing touch from close range after Butterfield had found Daniel in space on the left. Basham limped off and was replaced by Ahmedhodžić, but before United could reset defensively, DANIEL was left unmarked to head home a third for the home side.
Ndiaye replaced Osula at the interval and in the opening exchanges of the second period, Jebbison stung the palms of Dewhurst. The Blades were certainly looking to make a dent in the three-goal deficit, but Coulibaly could only fire over from Broadbent's low cross from the right. The pressure continued, but Dewhurst stood tall to save from Lowe, after good work from Fleck, before Jebbison backheeled wide on the rebound.
As the hour mark ticked by, Norwood replaced Arblaster and could have scored minutes later, after Norwood had robbed Taff high up the pitch. United had got Scunthorpe pushed firmly back now, but Lowe failed to hit the target from Norwood's inviting centre. At the other end, Amissah was alert to deny Fleming.
Shortly after a flurry of United changes, one of them, in the shape of BREWSTER gave them hope, as headed home from Baldock's cross from the byline with 16 minutes remaining and five minutes later after Baldock had won a header, NDIAYE rifled home from the edge of the area to give them further hope.
United galvanised by the six substitutions were sensing a draw, but after Dewhurst failed to collect under pressure from Berge, Brewster blazed over and unfortunately that was the last real chance of netting an equaliser.
Blades: Amissah, Broadbent (Baldock 73), Basham (Ahmedhodžić 40), Egan (Gordon 73), Robinson (Clark 73), Lowe, Arblaster (Norwood 63), Coulibaly (Osborn 73), Fleck (Berge 73), Osula (Ndiaye 45), Jebbison (Brewster 73).
Unused: Wharton.