Nigel Adkins acknowledged United's performance in Tuesday's loss against Bury at Gigg Lane 'lacked quality'.
Reflecting on a first away loss since the end of October, Adkins conceded the Blades had missed another opportunity to make ground on the teams above them in the table.
He remarked: "We went to Bury in confident mood following the win at Doncaster and made a bright start.
"We were forced into making a change with Chris (Basham) replacing the injured Neill Collins and I hoped that would allow us to pass the ball more, but we lacked quality and that was disappointing because could have dominated possession.
"Bury score at a crucial time, it was a fantastic strike from the lad, but there was a clear handball in the build-up and the referee misses it."
The Gaffer added: "We looked to be positive with the introduction of the likes of Billy (Sharp) and Matty (Done) and we were always trying to win the game.
"Che (Adams) had a shot cleared off the line and Bash had a great opportunity, as did John (Brayford), it comes down to fine margins but it wasn't the result we wanted or needed.
"We were determined to win the game and the repercussions because we haven't done are that everyone is bitterly disappointed and frustrated."