Chris Wilder was understandably hurting and frustrated, after the Blades were harshly denied deserved a point against Middlesbrough because of a disallowed goal in stoppage-time.
Video replays showed Jack O'Connell was onside from Mark Duffy's late free-kick, but the assistant referee raised his flag and the goal was chalked off to condemn the Blades to a first loss since January.
And Wilder wasn't impressed, remarking: "Myself, all our supporters, Danny Higginbottom, Jimmy Floyd Hasselbaink, they were decent players, honest boys with good opinions and decent standing in the game, know it's a decision that's costs us.
"I am not saying we came here and steamrollered Middlesbrough, because everyone keeps telling me about the Championship and sometimes you can't get overawed when you look at the teamsheets, but I don't want that to be us.
"I believe we deserved something for our second-half performance and regardless of how the goal goes in at the death, it goes in, it was a great piece of play and we were all off the bench.
"It would have been a great point at the home of the favourites, four points from two matches and I've got a lot of disappointed players and staff and no doubt supporters at the game and back home will feel we've been robbed of a point."
The Gaffer added: "We worked hard for this unbeaten run, the majority might not have been in the Championship, but we got ourselves in the game by changing things at half-time and I thought the goal was coming.
"We were the dominant force in the second-half, Duffy and Ched made an impact and Couttsy was tremendous, Boro had to change their shape to stop us.
"It is a massive, massive decision that's gone against us, but we have to take it on the chin."