Against the odds, the Blades picked up point which could prove vital in the final reckoning.
Playing with ten men for more than 70 minutes after Jose Baxter's sending off, the Blades trailed 2-0 with 15 minutes remaining.
But goals from Michael Doyle and Jamie Murphy in the space of less than two minutes, both at the Kop end, gave United a share of the spoils.
Boss Clough made three changes. McEveley, Campbell-Ryce and Baxter returned to the starting line-up. Kennedy and Reed dropped to the bench and the injured Holt missed out.
The Blades struggled for early rhythm. Harris was booked on five minutes for tugging back O'Brien and after a patient Coventry build up Samuel showed a lack of composure from Tudgay's knock down, O'Brien also fired wide from distance.
United's first assault on Coventry's goal arrived on 12 minutes and was the result of Baxter's 40-yard wide pass to Campbell-Ryce. The subsequent cross was perfect for Doyle, but the skipper missed his kick and from the follow up Harris drilled at goalkeeper Jones.
The game burst to life on 18 minutes with a flashpoint that left United numerically disadvantaged. A Baxter challenge on Barton in midfield resulted in the Coventry players surrounding the referee and even boss Pressley entered the field to display his displeasure. Referee Drysdale took his time but saw fit to show Baxter the red card.
A period of organisation saw the Blades keep Coventry quiet for 10 minutes and even went close with a long-range Murphy effort but the visitors grabbed the lead on 33 minutes. Goalkeeper Jones released quickly after a corner, SAMUEL got a fortunate ricochet and held off Doyle before sliding under Turner's body.
As half-time approached the visitors used their advantage to keep possession and look more of a threat. Phillips fired over the top and Turner produced a tremendous save on 40 minutes, using his body to block from Samuels, who connected with a Fleck cross.
In the third and final minute off added time at the end of the first half United almost caught City on the break. Brayford began the move and Harris and Murphy were involved before Coutts curled just wide of the left post.
Kennedy was introduced at the start of the second period, forcing a reshuffle involving Basham and Coutts, but United's plans to get back in the game were hampered by a second Coventry goal on 47 minutes. Phillips delivered a cross from the right, SAMUELS saw his first effort blocked by Turner but he had the space to ram the rebound into the roof of the net.
The goal enabled Coventry to redouble their efforts to slow play down further, whilst the Blades were failing to create many efforts to get back in the game, although Harris tried his luck from distance.
Turner saved from Thomas after Basham gave away possession and Tudgay's 25-yard shot was wide. Freeman replaced Coutts and he was involved in a great chance on 76 minutes, Pennington's short back pass was seized up by Done, who exposed the goalkeeper with the pull-back but it was just behind the onrushing Freeman.
The fun, though, was just about to start. On 78 minutes, Freeman's cross found Done, but his effort was blocked on the line by Pennington but in the second phase Murphy laid off to DOYLE, who dinked over Jones and into the net.
And under two minutes later the Blades were level. Doyle was prevented from getting a shot away from Brayford, but Done laid off to MURPHY, positioned on the edge of the box, and his shot beat Jones low to his right.
With ten men, United looked the team more likely to score late on and the initiative remained with the Blades in six added minutes. Chances, however, limited, the best a volley from Doyle, which was wide, but Clough and co. would have settled for a share of points with 15 minutes remaining.
Blades: Turner, Harris, Brayford, Basham, Doyle, Murphy, Baxter, Done (McNulty 86), Coutts (Freeman 70), McEveley, Campbell-Ryce (Kennedy 45).
Unused: Willis, Davies, Reed, Adams.
Coventry: Jones, Fleck, Williams (Thomas 58), O'Brien, Samuel, Barton (Finch 53), Phillips, Tudgay, Martin, Pennington, Stokes (Haynes 73).
Unused: Burge, Webster, Jackson, Turgott.