A colossal defensive performance enabled the Blades to make it eight clean sheets on the bounce.
United could not make it 11 successive wins at promotion-chasing Preston North End in front of the Sky Sports cameras but battled doggedly for a valuable point.
Preston had the better of the chances but time and time again the Blades made blocks and tackles to prevent the home side from ruining Mark Howard's shut-out run.
Freeman made his full debut for United in front of the Sky Sports cameras, slotting in at right-back - he replaced fellow loanee Davies, who dropped to the substitutes' bench, as boss Clough made one change from the 1-0 victory over Carlisle United.
Howard's run of clean sheets was severely tested inside 30 seconds. He saved but could not hold a volley from Davies but recovered to smother as Garner looked to pounce on the loose ball. The visiting side's defence was put under pressure on a number of occasions in the opening exchanges and a 25-yard free-kick from former Blades loanee Gallagher was just over on 14 minutes.
For United, Murphy cut inside and sliced wide from distance but it was a brief respite as the home side continued to force the Blades back. Garner just failed to connect with a pacy Humphrey cross from the right and there was also a penalty appeal that was turned away. Harris did well to block from Garner and Maguire was forced to kick away a Gallagher cross.
On 32 minutes, the Blades had the ball in the net, unfortunately it did not stand. Coady broke from midfield and was the one to put in the net after a move involving Murphy and Flynn but the loanee was adjudged to be offside as he planted the ball past goalkeeper Rudd.
Once again, though, North End responded as a Davies shot was deflected for a corner, which was to pave the way for a triple effort from the home side. Garner's headed was blocked by Harris, Doyle then got in the way of Wright's shot before Howard saved Gallagher's powerful follow up.
For all their attempts going forward, Preston looked worried when the Blades stepped over the halfway line. Coady almost got on the end of a Murphy cross when the Scot went around Wiseman and then a drive from Harris was blocked. Unfortunately it was the last contribution from Harris, who limped off soon after and was replaced by former Preston defender Hill, who received a warm applause from the home fans.
Just before the break a shot from Baxter was comfortable for Rudd but the Blades striker was laid flat out on the turf as the half-time whistle blew following a tough challenge in midfield.
Baxter re-appeared for the second half and but the Blades were forced into another change, Hill did not return which saw Davies introduced and Freeman switched to left-back.
United looked promising at the start of the second period but the chances were still falling Preston's way. On 55 minutes Brownhill found space on the left but struck a post and Garner headed over a Buchanan cross.
Neat feet almost found Scougall space but the Preston pressure continued and there was another nervous moment when Garner's shot from a Humphrey cross crept just wide of Howard's far post.
A couple of corners, with Maguire popping up at the back post, kept the home defenders on their toes, whilst a slip by Rudd almost gave Murphy an opportunity as the game entered the final 20 minutes. Gallagher did finally put the ball in the back of the net on 74 minutes but both he and Garner were offside and Clough then used his last change with Porter taking over from Baxter.
Tired legs were again coming into play and Preston made a double change. Into the last ten minutes, a Holmes cross saw Howard punch out and Doyle block the follow up from Gallagher. Moments later a Holmes corner was flicked to the back post but Gallagher's header was held under the crossbar by the hard-working Blades goalkeeper.
On 87 minutes a Davies cross was headed over by Porter and after Preston's umpteen penalty appeals it was United's turn to be denied a spot-kick in injury-time when Clarke and Maguire clashed.
Four minutes of added time was announced and the Blades, like the previous 90, protected Howard's goal and the hugely vocal Unitedites in the away end went home with a precious point.
Preston: Rudd, Clarke, Wright, Humphrey (Holmes 78), Gallagher, Garner, Buchanan, C. Davies (Beavon 78), Brownhill (K. Davies 85), Wiseman, Kilkenny.
Unused: Stuckmann, Keane, Welsh, King.
Blades: Howard, Harris (Hill 41, B. Davies 45), Maguire, Flynn, Doyle, Baxter (Porter 74), Collins, Coady, Scougall, Murphy, Freeman.
Unused: Miller, McGinn, Paynter, Long.