Greg Halford scored twice for Sheffield United as they came from behind to beat Leyton Orient at Brisbane Road.
JJ Melligan put Orient ahead from the penalty spot just before half-time after Matthew Kilgallon had handled.
But United turned things around as Halford hooked home following a goalkeeping error, and Darius Henderson set up Billy Sharp for the second.
A breakaway goal from Kyle Naughton made it 3-1 and Halford headed a fourth to set up a home tie against Charlton.
Leyton Orient manager Martin LIng:
"It was the old fashioned game of two halves. Obviously I was very happy with the first-half performance.
"We played with a tempo and a purpose and matched them in all departments to get our noses in front. Then the second half was not what we were asking for by a long way.
"They are a good side, I cannot deny that but I just feel we gave them a helping hand in too many departments and if you give help to a team like that you get the result that we got."
Sheffield United manager Kevin Blackwell told BBC Radio Sheffield:
"We were absolute garbage in the first half. We were still in the hotel, still on the bus and we deserved to be 1-0 down, maybe two.
"I had a few words at half-time and that was the response I was looking for. I thought in the second half we were a lot more professional. We were more positive. There had been no urgency about our play.
"I want ambition from everybody. Every game is there to be won. No disrespect to Orient, I demanded exactly the same today as I would against Watford on Saturday and I am pleased with the response."
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