Blades boss Chris Wilder admitted a poor second-half showing was ultimately the decisive factor in a disappointing loss at Walsall on Saturday.
After Jack O'Connell had cancelled our Amadou Bakoyoko's opener, three goals without reply after the break saw the Saddlers run out comfortable winners.
And Wilder didn't offer any excuses following a first loss in seven league matches, he remarked: "We didn't see that second-half performance coming and it simply wasn't good enough.
"We conceded some terrible goals and didn't deserve to win the game of football, we defended very poorly as a team and if you defend how we did then you open yourself up for the opposition to take full advantage and Walsall did.
"I thought we were dominant in the first-half and was bitterly disappointed not be in front at the break.
"Walsall were dangerous again on the counter attack as they were at Bramall Lane and obviously they caught us early on after Billy hit the bar."
The Gaffer continued: "But we responded and having equalised, missed two or three good chances to get our noses in front and 1-1 didn't really reflect the game in my opinion.
"The second goal is very poor defending on the counter attack and it shouldn't go in and the same applies to the third, so that's something for us to address in house.
"It is by far and away the worst we've defended and when we don't defend properly both individually and collectively we'll get punished and lose games."