The Blades were beaten 2-1 in their fifth-round replay at the KC Stadium after Kyle Naughton was adjudged to have headed into his own net.

Naughton misdirected his header as he tried to clear behind his own line and watched in horror as it thundered against the bar and bounced down onto the line.

A flag was quickly raised and the goal given but replays were inconclusive and Blackwell claimed the decision should never have been made.

"We have lost a game we haven't lost," Blackwell said. "That's one for the record books isn't it?

"The first goal isn't a goal. They can stand here and try to persuade me until they are blue in the face, but that isn't a goal.

"The official has made a decision and he is not 100% sure - that is what is the disgrace.

"Somehow we have lost and I don't know why it is."

The Blades managed to claim an equaliser through Billy Sharp after Naughton's 24th-minute blunder but Peter Halmosi settled the game in Hull's favour after the break.

There was further controversy, however, with United denied a penalty after Sharp was apparently tripped by Kamil Zayatte.

Blackwell added: "I think when officials have as poor a game as that they should be made to face the reporters, as we are, and asked why those decisions are made.

"They are key decisions - managers can lose their jobs over them.

"Fortunately we are in a good position but, if I was hanging on for dear life, that could have cost me my job.

"I have got a family and kids and that's what I find a disgrace. I'm frustrated."

Hull boss Phil Brown, whose side face a crucial Barclays Premier League clash with Blackburn on Sunday, was happy to accept the stroke of fortune.

Brown said: "The shoe has been on the other foot many times this season.

"I am happy because we have won the game, not because of refereeing decisions.

"We have been done at that twice this season, inconclusive goals, and one has gone our way tonight.

"When Billy Sharp goes down and the referee blows his whistle, your heart is in your mouth - but he's booked him, so he obviously thought it was a dive.

"Again, that decision went for us tonight.

"But the bottom line is you can't argue with the difference between the two teams.

"There was the little bit of quality in front of goal with Peter Halmosi's goal.

"Sheffield United had two shots in the second half and did not hit the target. The goalkeeper had no saves to make."