"I enjoyed it, enjoyed watching my team," said Wilder. "We played smart, and took our chances when they came along.

"At The Den it's real, it's raw. They say not nice things about you.

I got sent off as a 19-year-old kid here for Sheffield United, for a two-footed challenge, I'm not proud of that!

"But they ask questions of you always here. They've beaten better sides than us. You have to be up for it, you have to be at it, and I thought my players were.

"It looked pretty comfortable in the end but it was a very dangerous game for us. And I'm delighted with my players.

"It was everything you want as a manager. When opportunities come you have to take them, and I thought Mo's goal was fabulous.

"So I'm delighted we're in the hat on Monday."

Captain Billy Sharp led United's line adeptly with a battling performance, and was rewarded with a hand in Besic's fine strike.

"The skipper's been excellent, he's knocked on the door," said Wilder.

"His performance against Man City was good. And it was a good performance today against two strong centre halves on a difficult pitch."

Millwall boss Gary Rowett admitted his side were undone by two rare moments of quality in a stodgy affair, praising the Blades' attitude and application.

"I think it was a fair result in the end, up until 60 minutes of that there was an awful lot in the game but it was mostly between both boxes," said Rowett.

"We just lacked a bit of quality today that was all. We huffed and puffed and tried to force the ball into areas.

"You're hoping a Premier League team comes here disinterested. But you're never going to get that with a Chris Wilder team.

"You're getting a team with a brilliant mentality, and then the difference comes down to quality.

"Once we conceded the second one you know it's game over.

"Overall just a little disappointed we couldn't make more of a game of it."