Danny Wilson was left 'bitterly dissapointed' after seeing his side drop two vital points at Notts County on Saturday.
Already leading courtesy of a second minute header from Harry Maguire, United saw County striker Francois Zoko dismissed before the break for foul and abusive language.
But a below par second half showing culminated in Alan Judge rescuing a point for the hosts ten minutes from time, much to the annoyance of the Blades boss.
Speaking afterwards, Wilson commented: "In the second half we didn't do anywhere near enough to make the win comprehensive despite our lead and numerical advantage.
"We are bitterly dissapointed because we have invited pressure ,dropped too deep and haven't press the ball like we did in the first half.
"At 11 v 11 we played with a real good tempo, but we surrendered our advantage by letting them get back into the game.
"At half time I told the players their chances would come from long balls and free kicks and we conceded a silly one and paid the ultimate price.
"What annoyed me the most though is we have allowed the smallest lad on the pitch (Judge) to get his head on the ball."
Analysing the performance in further detail, the Gaffer added: "There is a real nervousness about us in three or four areas, perhaps it is down to pressure , but we didn't keep hold of the ball and pass it as we know we can.
"We were hitting the ball forward and it wasn't sticking, we need someone to get hold of the ball and calm things down.
"I know we will get back to the form we showed in the first part of the season, but we should have made the most of the situation that presented itself today and we haven't."