David Weir was left ruing individual errors as his team slipped to a 3-1 defeat to Rotherham United at the New York Stadium.
Jose Baxter, with his first goal for the club, gave the Blades a deserved lead at the interval, but three goals in 24 second-half minutes for the hosts condemned United to a third straight league loss on the road.
Speaking afterwards, Weir offered no excuses and was clearly angered by how his players undid their good work of the first period.
He commented: "I am massively dissapointed with the result and how the game turned out in the end.
"In the first-half we had a lot of the ball and played really well. We thoroughly deserved to be ahead at the break.
"We were dominant and created a lot of opportunities, I thought we looked comfortable and I expected us to build on that.
"But in the second-half we made some really poor mistakes and it is bitterly disappointing and very frustrating to lose in the manner we did.
"The disparity between the first-half and second-half showing was massive and you can't legislate for three individual errors."
Weir added: "Rotherham came out positively as we expected but we didn't respond at all and the manner of the goals we conceded is something beyond my control.
"There aren't any positives immediately after losing a game in the way we did and I can fully understand the frustration of our fans."