Danny Wilson remained in philosophical mood despite Saturday's 2-0 home defeat at the hands of Yeovil Town.
A second-half Paddy Madden double condemned the Blades to a second straight defeat at Bramall Lane and afterwards Wilson refused to make excuses.
He said: "We haven't said this often this season but that performance was a big disappointment.
"Certain parts of the team didn't function and we weren't positive enough.
"We have had chances and not scored, we had fantastic opportunities in offensive areas and declined them and in general we were too slow on the ball.
"We need to learn and quickly, but you have to expect the odd mistake, especially when several lads are in the infancy of their careers.
"Sometimes you pay the price and we have on this occasion."
Analysing the two goals United conceded, the Gaffer felt both were avoidable.
He added: "The first goal was a bad defensive slip and I am talking about the whole back four.
"The second one was something of a freak but these things happen in football and George (Long) will comeback stronger from that experience."