A moment of quality from Dave Kitson helped the Blades to a fourth consecutive away league win.
Just before the break a deft lob from the big striker was the difference between the United and Preston North End.
Danny Wilson's side produced a workmanlike performance at Deepdale to ensure the unbeaten start continued, although a big, late save from George Long was required!
Boss Wilson made five changes from the midweek JPT win, with Blackman, McDonald, Kitson, McAllister and McMahon returning. The team showed just one alteration from the last league fixture - McAllister replacing Cofie, who dropped to the bench and was joined by the fit-again Collins. The home team included former Blades Academy defender Robertson, whilst goalkeeper Simonsen, was on the bench.
It was quickly evident that McAllister was to slot into a wide midfield role as United continued with the preferred 4-4-2 system. The first attempt on goal was half-hearted, Welsh firing over for Preston - for the Blades, Kitson saw a lot of ball early on, getting in on action as Flynn won a free-kick on eight minutes but Maguire's flicked header from the subsequent set-piece was over the crossbar.
From Wroe's corner, Beardsley was unmarked as he headed over Long's crossbar, whilst Welsh hit a first-timer wide as the battle for midfield supremecy continued through the half-hour mark. Blackman and McAllister linked up a couple of times on the right but the Blades were unable to open up the home side... until the referee's watch ticked around to 43 minutes.
McMahon's clipped ball from the right ensured the Preston central defenders were turning but KITSON outpaced them both, taking a steadying touch to assess the situtation ahead of executing a perfect lob, which beat Stuckmann and nestled into the net after kissing a post.
It was one of the few moments of quality throughout the first period and deservingly gave the Blades a slender half-time lead but the goalscorer did not come out for the second half and was replaced by Porter.
Early in the second period, Hill cut out a Wroe pass which looked like putting Beavon in the clear and then the ex Preston defender also won a header when Beardsley was setting himself. At the other end, Blackman shot wide on the turn after another ball over the top by McMahon had both strikers chasing.
The intensity had been turned up - both sets of fans playing their part with vocal backing - and the chances continued. On the hour, from Blackman's cross, Robertson smacked the ball against his own post and for the home side, Beardsley volleyed wide from a Monakana cross.
Hill was very busy, he toed away when Beavon was ready to shoot, whilst a neat turn from Monakana engineered a shooting chance that was not far wide on 70 minutes.
Collins was introduced as an insurance policy, whilst twice in the space of a couple of minutes Blackman was a threat. His first effort was blocked and his second, after dancing around Laird and Robertson, was saved by the goalkeeper's legs.
United's entire back line, plus the men in front, were overworked late on and Miller was brought on to take the place of Blackman and was instantly involved - the substitute looked like he was about to latch on to a punt forward when he was caught by Robertson, who appeared extremely lucky to receive a yellow card rather than a red.
From a Preston corner on 89 minutes, a Blades break saw McDonald find the sprinting Williams but he was off target with his first time effort and soon after it was signalled that four minutes of added time would be played. Goalkeeper Stuckmann went forward for a late free-kick and Hill was booked for a crude challenge but there was late drama when, in the fourth minute, Long made a terrific one-handed save from Huntington and then recovered to punch clear...effectively sealing the win.
PNE: Stuckmann, Keane, Laird, Robertson, Wroe (Sodje 72), Monakana, Welsh, Beardsley (Amoo 64), King, Wright (Huntington 57), Beavon.
Unused: Cummins, Byrom, Procter, Simonsen.
Blades: Long, Maguire, Hill, Flynn, Doyle, Blackman (Miller 84), McDonald, Kitson (Porter 45), McAllister (Collins 76), McMahon, Williams.
Unused: Westlake, Cresswell, Cofie, Willis.