A controversial own goal by Kyle Naughton and a Peter Halmosi strike handed Hull a 2-1 win and a place in the FA Cup quarter-finals on Thursday night.
Hull took the lead for the first time in the fifth-round tie when Naughton was ruled to have headed into his own net after 23 minutes of the KC Stadium replay.
TV replays were inconclusive and suggested he might have been unlucky and, despite an equaliser from Billy Sharp, there was no repreive as Halmosi settled affairs in the second half.
It was a spirited effort from the Blades, who almost grabbed the lead after four minutes when Greg Halford, again deployed as a makeshift striker, almost repeated his early goalscoring feat from the 1-1 draw between the sides on February 14.
The on-loan Sunderland defender met a looping cross from Brian Howard with a firm header but could not direct his effort on target.
Hull responded well and threatened to make the visitors pay for the miss in a strong 15-minute spell that saw Naughton, in particular, endure a torrid time.
Naughton was fortunate to escape being sent off after 18 minutes when he bundled over the onrushing Halmosi on the edge of the box and referee Peter Walton showed only a yellow card.
And Naughton handed Hull the lead moments later. He appeared in little danger as he positioned himself under Nathan Doyle's cross but his backward header thundered against the bar, bounced onto the line then struck the woodwork again.
To their credit, the Blades responded positively and were back level just eight minutes later. Halford was again involved as his cross from the right was headed back by Lee Hendrie and then stabbed home from close range by Sharp.
Hull looked to reassert their authority early in the second half and they got their noses back in front in the 56th minute when Halmosi ghosted in and slid the ball across Paddy Kenny and in at the far post.
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