Chris Wilder was critical of his team following Saturday's draw against Rotherham United.
Goals from Mark Duffy and Chris Basham twice put the Blades ahead, but Jamie Proctor's goal in stoppage-time recused a point for the home side.
And afterwards, Wilder admitted it was the least the Millers deserved, he remarked: "The performance wasn't good enough, but full credit to Paul (Warne) and his team.
"They were the better side in and out of possession, they won more first and second balls, they looked hungrier than us and their equaliser at the death summed our performance up really.
"We nearly got away with one, because we didn't play well, apart from the goalkeeper. We could have made any changes really, we changed the shape three or four times.
"We were very, very poor, but let's compliment the opposition, I'd have been disappointed with not getting win if I were in their changing room."
Wilder added: "We sent the warning signs out to the players, we did our preparation and told them what was coming, but we played too short and dipped our toe into tackles.
"We played in the wrong areas, we played our own game when we should have recognised the need to miss out the midfield at times when under pressure.
"Disappointing too many perhaps came here expecting a comfortable afternoon, it's not been a good day.
"I won't hide behind the point, we didn't do enough to win the game, but there were four or five mistakes that contrive to the second equaliser."