Jamie Murphy scored United's 7,000th league goal in this Sky Bet League One encounter with Leyton Orient.
Murphy levelled a first half goal from Dean Cox as United against tested themselves against another promotion contender.
The Blades, in their 50th competitive fixture of the campaign, were the better side in the second half but had to settle for a point.
Maguire and Porter returned as boss Clough made two changes for the home encounter with Leyton Orient, Davies and Paynter dropped to the bench and were joined by defenders Harris and Hill, both back after injuries.
The early exchanges saw Collins commanding, winning a number of headers, whilst further forward Coady was employed as the more advanced central midfielder in support of Porter. The opening 15 minutes brought little in terms of scoring opportunities, Murphy and McGinn went for the same Brayford cross and then the Blades wall blocked a free-kick from Ness.
An inviting Odubajo cross evaded his team-mates as the lack of chances continued through the mid-point in the first half and United's appeals for a penalty, following Cuthbert's challenge on Coady, were waved away.
As half-time approached goalkeeper Jones punched away Brayford's dangerous cross and Freeman went on a mazy run before Leyton Orient took the lead on 41 minutes. Following two long-range Lundstram shots and the ball bouncing around the Blades box, COX coolly lifted the ball over Freeman to give himself the space required to slot under Howard
Before the half-time whistle, the Blades registered a couple of chances, through Brayford, the right-back volleyed wide with his unflavoured left boot and then attached himself to a cross, whilst Maguire picked up the game's first booking for a foul on Cox.
The Blades were the more adventurous in the early stages of the second period. After Coady was fouled, Murphy's free-kick was deflected over and from the resulting corner a Brayford shot was blocked by Omozusi.
In the space of five minutes Clough made two tactical substitutions with Scougall and Davies taking over from McGinn and Porter, which gave Murphy the central striker's role - and it paid immediate dividends.
With 63 minutes on the referee's watch the Blades levelled. A through ball from Davies beat Baudry and Murphy raced clear before rounding Jones to slot into an unguarded net from an acute angle.
Scougall fired at Jones after a quick free-kick and the Orient goalkeeper was being tested, he had to push over a Coady shot on 69 minutes. Soon after a Davies free-kick was headed wide by Brayford and Clough's last change on 77 minutes, was Harris replacing Freeman.
Jones was called upon again to save and hold a Davies free-kick and in the final 10 minutes the away side came back into the game. Scougall was booked for crudely stopping Batt and then Collins was well-placed to block a Lisbie shot.
Despite Leyton Orient being third in the table, it was the Blades who looked the more likely to nick a winning goal in the four minutes of injury time. Flynn was unable to get a shot away following Scougall's cross and Davies curled over before the referee's final whistle signalled a second successive home draw against London opposition.
Blades: Howard, Brayford, Maguire, Flynn, Doyle, Porter (Davies 63), McGinn (Scougall 58), Collins, Coady, Murphy, Freeman (Harris 77).
Unused: Hill, Paynter, Long, Dimaio.
Orient: Jones, Omozusi, Cuthbert, Baudry, Cox (Mooney 70), James (Batt 83), Lisbie, Odubajo, Clarke, Lundstram, Ness.
Unused: Sawyer, Larkins, Gorman, Dagnall, Simpson.