A goal in each half saw United recorded another home win against Millwall on Tuesday night.
Jack O'Connell headed home the opener, before Kieron Freeman doubled the lead in the second-half as the Blades broke through the 80-point barrier to strengthen the grip on top spot in EFL League One.
For the rearranged fixture against Millwall, Lafferty, Coutts and Duffy all returned to the starting XI. Ebanks-Landell missed out with a minor ankle problem, whilst Done and O'Shea dropped to the bench.
Kicking towards the Kop, in a break to the normal routine, the game lacked any real goalscoring opportunities in the opening 10 minutes, although Moore had to be alert to cut out Ferguson's left-wing cross.
But after a spell of sustained pressure, the Blades took the lead in the 16th minute. From a third corner in quick succession, Fleck's inswinging delivery was headed home at the back post O'CONNELL, who scored for the second consecutive home fixture.
In the next attack, United went within in whisker of doubling the advantage. Lafferty, Sharp, Hanson and Duffy were all involved in the build-up, before Coutts forced a stunning save from Archer, who somehow tipped a thunderbolt of an effort over the bar. That was Archer's last action though as he left the field with an injury shortly afterwards.
With half an hour gone, Wright was the first name in referee Simpson's book, for a foul on the advancing on Wallace. United then had appeals for a penalty waved away as Freeman tangled with Ferguson and Williams. As the clocked ticked down towards half-time, Hanson headed wide from Fleck's cross, following more neat build-up play.
As four minutes of stoppage-time was, United crafted another chance, with Duffy and Coutts along with Fleck combining beautifully, before the latter shot wide with his right foot. Before the break, Thompson was shown a yellow card for a lunge on Fleck.
The second-half burst into life quite literally in the 55th minute. O'Connell's lung bursting run caused chaos in Millwall's defence and in the second phase, an advanced FREEMAN curled home a lovely effort past King to net his tenth of the campaign, much to the delight of the home crowd who erupted into full voice.
With 23 minutes remaining, Wilder made United's first change of the contest, with Carruthers replacing Duffy. United had a double scare shortly afterwards, Wallace freed Gregory, who should have scored. In the same incident, Moore appeared to be seriously injured, only to rise to his feet to applause after a spell of treatment.
The visitors were throwing everything at the Blades as the game entered the final 10 minutes and only a goal line block from Basham kept United's two-goal advantage in tact after Romeo had teed up Williams inside the box.
Five minutes of added time were signalled, but United saw them out without further alarm, to move seven points clear at the summit of the division.
Blades: Moore, Fleck, O'Connell, Basham, Sharp (O'Shea 84), Wright, Coutts, Hanson, Freeman, Duffy (Carruthers 67) Lafferty.
Unused: Long, Done, Wilson, Clarke, Chapman.
Millwall: Archer (King 26), Craig (O'Brien 67), Williams, Thompson, Gregory, Onyedinma (Morrison 51), Romeo, Wallace, Webster, Ferguson, Cooper.
Unused: Cummings, Hutchinson, Worrall, Butcher.