United deservedly advanced to the fifth round of the Emirates FA Cup, with professional performance against Millwall at The Den.
Mo Besic opened the scoring with a curling left footed effort just after the hour, before Ollie Norwood added a second to kill off the tie with minutes remaining.
For the clash against the Lions, boss Wilder made five changes from the starting XI which faced Manchester City in midweek, whilst Jack Robinson was named amongst the substitutes.
After a quiet opening few minutes, both sides had a chance within 60 seconds of each. Norwood freed Osborn down the left, he combined with Sharp and fired in a low cross, but Besic didn't trouble Bialkowski with a left footed effort from the edge of the box. At the other end, O'Brien got the better of Jagielka and wrong-footed O'Connell, but his shot was comfortable for Henderson.
The game lacked any real fluency on a difficult surface, but on 22 minutes the Blades came so close to edging in front. Basham turned 18 yards out and played in Sharp, he round Bialkowski, but Brown managed to get back and clear his effort off the line.
As half-time approached, O'Connell was required to block Mahoney's volley which looked to be on target, before Jagielka headed over at the back post from Norwood's left-wing corner, with the experienced defender appealing for a penalty under pressure from a retreating defender, but referee Taylor waved away his protests.
United were quickly on the front foot and gradually pinned the home side in. Robinson was close to turning home Sharp's header down from a Norwood cross, but in the 62nd minute the Blades hit the front. BESIC gained possession on the right, he dummied and shook off the attentions of a couple of defenders before curling home with his left foot past the despairing dive of Bialkowski.
Clarke replaced Callum Robinson and Kieron Freeman was booked for apparent time wasting, before O'Connell thought he had scored a second, heading home Luke Freeman's free-kick, but referee Taylor adjudged he had fouled his marker prior to making contact with the ball.
The home side were doing their best to urge the side on in a bid to force a replay, but NORWOOD fired home a fine second, rifling the ball past Bialkowski from 20 yards from Sharp's lay-off, with Osborn and Jack Robinson, who is debut, involved in the build-up.
The clock was ticking down in United's favour, but they had chances to add a third before the end. Clarke saw his effort beaten away by Bialkowski, before skipper Sharp was denied by the home stopper, but it was never going to have a major bearing on the outcome of the tie, as the Blades marched purposefully into the hat for the fifth round.
Milwall: Bialkowski, M Wallace, Cooper, Smith (Bodvarsson 71), Ferguson (Bradshaw 71), Pearce, Molumby, Brown, Mahoney (J. Wallace 73), O'Brien, Mitchell.
Unused: Sandford, Hutchinson, Romeo, Skalak.
Blades: Henderson, O'Connell, Basham, L. Freeman (J. Robinson 81), Sharp, C. Robinson (Clarke 67), Jagielka, Norwood, K. Freeman, Osborn, Besic.
Unused: Lundstram, McBurnie, Egan, Morrison, Verrips.
As it happened...
The action is underway, the Blades have kicked off and will kick from left to right in the first half.
United force the first corner of the game.
But Luke Freeman's delivery from the right is header away by Smith.
United pass the ball confidently forward, with L. Freeman, Osborn and Sharp all involved, but from Osborn's low cross, Besic fires a left footed wide.
At the other end, O'Brien gets the better of Jagielka and creates room for a shot, but Henderson comfortably save to his left.
The Blades on the attack again, forcing a second corner of the game.
But despite L. Freeman's inviting centre, a host of bodies fail to make a clean contact.
From distance, skipper Sharp then fires over with an ambitious effort.
So close for the Blades.
Some neat play around the box sees Basham play through Sharp, he rounds Bialkowski, but Brown clears off the line.
O'Connell makes a timely block to divert Mahoney's volley wide at the expense of a corner, which Henderson claims easily.
Another chance for United.
Norwood's corner from the left is headed over by Jagielka, but he feels he should have had a penalty for a shirt pulling.
It's goalless here at The Den at the break
The second half is underway, with the Blades kicking towards the travelling supporters.
Some early pressure from the Blades.
A couple of early crosses get the hosts retreating, but from K. Freeman's centre, Bialkowski claims.
Robinson denied under pressure from Cooper from Sharp's header towards goal.
United take the lead and it's a beauty from Besic that breaks the deadlock here at The Den.
The Bosinian delightfully curls home with a left footed effort from the edge of the penalty area.
Robinson is replaced by Clarke
K. Freeman is cautioned for time wasting in the eyes of referee Taylor
Double change for the Lions...
Bradshaw and Bodvarsson replace Ferguson and Smith
Jed Wallace enters the field, replacing Mahoney.
United have the ball in the net again.
But O'Connell is deemed to have fouled his marker before heading home L. Freeman's free-kick.
Jed Wallace beats Osborn on the left, but K. Freeman makes a vital defensive header at the back post with O'Brien lurking.
Jack Robinson is introduced for his Blades debut, replacing L. Freeman.
It's a second for United and it's another screamer.
Osborn, J. Robinson and Sharp are involved, but it's Norwood who fires home into the bottom corner from 20 yards
Clarke stings the palms of Bialkowski, as United look for a third.
There will be an additional three minutes added on
And the Blades come so close to making it three.
Sharp finds himself in on goal, but Bialkowski makes himself big to keep his effort out.
United break again but from a Besic pass, K. Freeman can't beat Bialkowski
United are through to the fifth round of the Emirates FA Cup.
Besic and Norwood both score from outside the penalty area to see off Millwall here at The Den!