An injury-time disallowed 'goal' left United with a sour taste in Saturday's encounter at Middlesbrough.
Dael Fry headed past his own goalkeeper but referee Peter Bankes, with the help of one of his assistants, ruled the effort out.
Earlier, Rudy Gestede had given Boro the lead.
Boss Wilder reverted to the starting XI that faced Brentford for the televised clash. On the bench, there was a change with Evans replacing Lavery.
There was little between the teams early on, although the initial opportunities dropped to the Blades. Clarke had time and space from Freeman's pull-back but his shot was blocked and Fleck almost wriggled clear but defender Fry added a vital touch.
Boro's first chance saw Bamford balloon a free-kick over from 25 yards but they grabbed the lead on 20 minutes. Forshaw's hook into the box saw Basham win the first header but GESTEDE reacted quickest to loop the loose ball over Blackman.
United were put on the back foot for a spell as Middlesbrough grew into the game. After a debatable corner, Clayton's purposeful deep corner saw Friend arrive unmarked at the back post but Coutts cleared at the expense of another set piece.
As half-time approached, Boro remained on top. From Christie's cross, Gestede rose above Basham but the striker's header struck the outside of a post, then Bamford curled just wide from the edge of the box and Forshaw sliced over a separate chance just before the interval.
Both sides won a corner early in the second period and the first chance of the half saw the home side's Howson fire over from 25 yards.
The Blades were seeing plenty of the ball in midfield but finding it difficult to penetrate the Boro defence. Duffy was introduced before the hour and he was involved in a patient build up to a good chance on 62 minutes - a low Stevens cross was presented by Clarke to Coutts, who controlled a side-footed effort which was heading to the bottom corner before Randolph palmed away.
For the final quarter, Evans took over from Sharp and quickly shot wide of the near post as United remained on top in terms of possession and territory. Boro, though, remained a threat and on 74 minutes Blackman saved from Christie.
Brooks was United's final throw of the dice, the youngster replaced Freeman, meaning a slight change in formation for the final ten minutes. The Blades continued to try and force a leveller. Late on Clarke's cross was blocked and from the follow up, his effort was saved at the near post by Randolph.
In injury-time, O'Connell won a free-kick from Christie and United thought they had levelled. Duffy delivered and as O'Connell challenged, Fry put the ball in his own net. However, the linesman on the dugouts side, who had earlier wrongly flagged Freeman offside, had his flag up again to disallow.
In the final minute, a Duffy volley was not far away but the final whistle blew with United feeling aggrieved.
Middlesbrough: Randolph, Friend, Gibson, Clayton, Assombalonga (Fletcher 79), Bamford, Howson, Fry, Christie, Forshaw (Leadbitter 84), Gestede (Baker 68).
Unused: Dimi, Fabio, Roberts, Traore.
Blades: Blackman, Stevens, Fleck, O'Connell, Basham, Clarke, Sharp (Evans 68), Coutts, Freeman (Brooks 79), Stearman, Carruthers (Duffy 57).
Unused: Lundstram, Wright, Lafferty, Eastwood.