Chris Wilder admitted Saturday's loss at Barnsley was a 'damaging result' in United's quest for a play-off place.
And although the Blades boss was encouraged by how his side came from behind to lead at Oakwell, he was bitterly disappointed in the manner of the performance their after, as goals from Oliver McBurnie and Tom Bradshaw won it for the Tykes, despite strikes from John Fleck and Leon Clarke.
The United chief remarked: "They started better and faster than us. The team fighting to stay in the division had more drive and desire than the team wanting to get out of division.
"We played too slow, we played backwards and square, they won more first and second balls and obviously they were the better team in the first-half.
"We changed a couple of things round and for 25 minutes of the second-half we dominated and showed the character we have within the group."
Wilder added: "We got ourselves level and then in front and from that point there should only be one winner.
"But we didn't get the third and fourth that would have demoralised the opposition, it's been like that for most of the season, let alone the last three games.
"We are a really good side at times, a really good side. But we've got to make sure we get the results our performances deserve, and this is another damaging result for us."