Nigel Clough offered no excuses following Tuesday's loss to already relegated Yeovil Town at Huish Park.
A lacklustre performance from the Blades was punished midway through the second-half when Stuart Arthurworrey got the final touch from Sam Foley's free-kick to ensure all the points stayed in Somerset, much to Clough's obvious displeasure.
Speaking in the aftermath of the defeat to Paul Sturrock's side, the Gaffer remarked: "It is an unbelievably disappointing result and performance, we have lost to another mistake.
"We were poor to a man, although you have to take John Brayford out of that. I thought he was outstanding. His desire and drive was greater than anyone else in a United shirt.
"We were lethargic, we looked mentally tired and it felt like a pre-season game in the first-half.
"The game was crying out for us to take the initiative, but we didn't we just sat back almost expecting something to happen and it doesn't work like that.
"When you don't go and try and win the game you are always vulnerable, Mark Howard hasn't been troubled all night, then he makes a small mistake and we lose the game."
The Blades boss was angered at his team's play in the final third and admitted afterwards it was a 'low point' of the season, now he is demanding a positive response against Bradford City on Saturday.
He concluded: "The players didn't take enough responsibility in creating chances and when we did get shots away they weren't on target.
"Stefan Scougall and Paul Coutts both wasted chances in the first-half and we had enough possession to make the situation easier for ourselves, but we wasted them.
"The lads know it wasn't good enough, they can only apologise which they have, but we need a reaction. This is a low point, 43 games into our league season, but in the past we have bounced back straight away."