Nigel Adkins admitted Saturday's loss against Millwall at Bramall Lane was a difficult one to accept, as he felt a number of key decisions went against his side.
A goal in each half from Aiden O'Brien secured the points for the Lions, despite substitute Jose Baxter equalising for the Blades with 20 minutes remaining and afterwards Adkins spoke of his frustrations.
He commented: "It was a good game, an entertaining one, but one that ultimately ended in disappointment.
"There were two fouls not given in my opinion in the build-up to their first goal, one on Done and a clear shirt pull by the lad who scores on Collins.
"At half-time we made a change that worked out well, Jose comes on and has an impact centrally as we allowed the full-backs to provide the width.
"We score a great goal from Kieron Freeman's cross and we looked dominant and the only likely winner.
"Then low and behold they go and score against the run of play, but again I don't know how the referee misses a clear foul in the build-up."
The Blades boss refused to blame the defeat on the match officials, but was nonetheless unhappy at one other incident in particular.
He added: "I am holding my words close to my chest because we got beat, but the challenge on Dean Hammond in the middle of the park is an horrendous one which went unpunished.
"We wanted a tempo about the game, but at times it was very stop start and some of the decision making was very inconsistent.
"I am an honest person, I am up front and first and foremost I look at myself and my players, but overall I was very disappointed with the performance of the officials."