Millwall bowed out of the Emirates FA Cup at the Fourth Round stage on Saturday afternoon as Sheffield United were 2-0 winners at The Den.
Mo Besic and Ollie Norwood struck in the second-half to end The Lions' interests in the competition.
Gary Rowett handed starts to Billy Mitchell and James Brown, whilst Shane Ferguson, Aiden O'Brien and Matt Smith also began the game in a 4-4-2 formation.
All four sides of The Den were in great voice as the game got underway, and the first chance went the way of Millwall, but Smith blazed over from distance.
With eight minutes on the clock The Lions had a real oportunity to open the scoring, but after O'Brien latched on to a pass from Jake Cooper and beat his man, his effort was weak and easily gathered by Dean Henderson.
The visitors, meanwhile, were able to get on the ball in the middle of the pitch but were unable to test Bartosz Bialkowski to date - Billy Sharp's wild effort, which ballooned well wide, the closest they had come.
The Blades did come extremely close at the midway point of the first-half, however, but after Sharp left Bialkowski in his wake and struck towards goal, Brown was well-placed to hack the ball off the line.
As the game wore on chances became fewer, but with 36 minutes elapsed the ball dropped to Connor Mahoney on the edge of the penalty area; his volley was blocked behind by Jack O'Connell, though. Two minutes later, veteran Phil Jagielka had the chance to nod United in front, but after he met a corner-kick he nodded wide, despite his protests for a penalty.
Ten minutes into the second-half a deep cross worried The Lions and found Sharp at the back post, but his prod towards goal was turned behind by Alex Pearce despite the attentions of Callum Robinson. Kieron Freeman then tried his luck on the volley but the ball went well wide.
A momentary scramble inside the penalty area then saw an O'Brien shot blocked, but with 62 minutes played, United took the lead as Besic curled home from the edge of the penalty area and past the despairing dive of Bialkowski.
Rowett made a double change with just under 20 minutes remaining, bringing on Tom Bradshaw and Jon Dadi Bodvarsson, with Jed Wallace following shortly after, but it was The Blades who had the next opportunity as O'Connell headed into the net; Anthony Taylor, however, judged there to have been a foul in the build-up.
Jed Wallace had only touched the ball twice since coming on, but both times he beat his marker - the second time saw the winger fizz a ball into the box, but outstanding defending from Kieron Freeman prevented O'Brien from getting to the ball at the back post.
Six minutes from time, though, Norwood struck from distance to double The Blades' lead.
Substitute Leon Clarke had the chance to make it three not long after but his effort was well stopped by Bialkowski, with the stopper again rescuing Millwall from a further deficit in stoppage-time as he saved from Sharp's close-range attempt.
Millwall: Bialkowski, M. Wallace, Cooper, Smith (Bodvarsson 71'), Ferguson (Bradshaw 71'), Pearce, Molumby, Brown, Mahoney (J. Wallace 73'), O'Brien, Mitchell. Subs not used: Sandford, Hutchinson, Romeo, Skalak.
Sheffield United: Henderson, O'Connell, Basham, L. Freeman (J. Robinson 80'), Sharp, C. Robinson (Clarke 67'), Jagielka, Norwood, K. Freeman, Osborn, Besic. Subs not used: Verrips, Lundstram, McBurnie, Egan, Morrison.
Scorer: Besic 62', Norwood 84'
Booking: K. Freeman
Referee: Anthony Taylor
Attendance: 12,653 (1,443)