A battling and committed performance helped the Blades hit the summit of League One.
Tuesday's 0-0 draw at Swindon Town - one of Danny Wilson's former clubs - helped United leapfrog over previous leaders Tranmere Rovers, who did not play.
Swindon hit the woodwork twice but the Blades recorded an eighth clean sheet in the league to protect a point.
Hill recovered from a dead leg, sustained at the weekend, to continue and the only change to the starting line-up was on the left where Williams replaced Miller, who dropped to the bench and was joined by 18-year-old homegrown defender, Kennedy.
The preferred formation of 4-4-2 was employed as a spell of early defending was required - the home side won a corner in the first minute and soon after a long-range half-volley from Ritchie clipped the top of Long's crossbar. United's first attempt was a header from distance by Porter, which was comfortably gathered by Foderingham.
From their second corner, Swindon went close again - this time United half-cleared but from Ritchie's ball back into the penalty area a flicked header from striker Collins was just wide. As the Robins made an intense start Ritchie also fired over on 22 minutes.
A block from United's Williams, no less than 25 yards out, powered towards Swindon's goal but Foderingham was well-placed and the home side soon hit back. On 29 minutes, from a Roberts pass, Ferry found space on the edge of the box but Long turned the ball around the post. McMahon and Long then dealt with subsequent dangerous corners.
United did well to nullify the home side's threat as the half progressed. The only moments of note in the last 15 minutes before the break was a yellow card for one of Swindon's Thompsons for a crude challenge on Williams, whilst Devara headed wide a corner.
The first effort of the second half was a header from the home side's Collins but he was off target, although Roberts went closer on 54 minutes when his deflected shot struck a post - the rebound cannoned away to safety, fortunately from United's point of view.
United's first chance of the second half was Hill heading wide a Flynn cross and with 20 minutes to go Cresswell replaced Blackman to add fresh impetus. From a Thompson cross the two Collins's went up for a header with the Swindon striker heading just wide.
As the game entered the final ten minutes the chances were drying up as both sides were keen not to make a mistake. A yellow card was shown to McMahon, the referee presuming he was attempting to slow a Swindon throw, but the best Blades chance came in the 90th minute. From a McMahon free-kick, a Collins effort was kicked off the line and, from the rebound, a Maguire shot was blocked.
There was still time for Long to rush off his line to prevent Swindon's Williams connecting with McMahon's underhit back pass and a long range McDonald shot before the referee called a halt with honours even.
Swindon: Foderingham, McEveley, Devera, Ferry, J. Collins (Storey 74), Ritchie, Roberts (De Vita 66), N. Thompson, A. Williams, L. Thompson (Archibald-Henville 87), Ward.
Unused: Bedwell, Benson, Rooney, Oakley.
Blades: Long, Maguire, Hill, Flynn, Doyle, Porter, Blackman (Cresswell 71), McDonald, N. Collins, McMahon, M. Williams.
Unused: Westlake, Miller, McAllister, Cofie, Kennedy, Willis.