Millwall suffered a defeat as the 2019/20 Sky Bet Championship campaign resumed on Saturday afternoon as Derby County were 3-2 winners at The Den.
Matt Smith gave The Lions an early lead, but Louie Sibley's hat-trick turned the game on its head and gave The Rams all three points.
Jon Dadi Bodvarsson netted a late consolation with the benefit of goal-line technology.
Gary Rowett opted to start with Smith up front, with Ryan Leonard just behind him. Jed Wallace and Shane Ferguson occupied the wide areas, with Ryan Woods and Jayson Molumby sitting in front of the back four, which consisted of Mahlon Romeo, Shaun Hutchinson, Jake Cooper and Murray Wallace.
After the pre-match formalities were complete, a new and historic era began as the game kicked off - and after the visitors, in particular Wayne Rooney, had the ball in the early stages, the first chance went the way of Millwall - and it resulted in a goal.
Jed Wallace received the ball from Ferguson, who in turn fed Murray Wallace; his pass found the Northern Irishman, who curled a delicious ball for the awaiting Smith to power home a header at the back post.
Three minutes later it was Louie Sibley who had The Rams' first effort of the afternoon, but Bartosz Bialkowski was well placed to fist the ball away. Derby then fashioned a free-kick in a promising position, but fortunately ex-Lion Martyn Waghorn's effort clipped the crossbar before going over.
On 26 minutes, however, The Rams were level after Sibley's determination saw him battle past the defence before poking an effort into the roof of the net.
Romeo's drive from afar was then spilled by Ben Hamer before being cleared to safety, with Jed Wallace's cross-cum-shot nearly deceiving the stopper moments later - Hamer gloved behind, however.
Sibley was causing The Lions problems and with 10 minutes until the break he once more looked to dance through the defence and shoot, however this time Bialkowski was able to claw the ball from nestling in the back of the net.
With half-time approaching Romeo struck a left-footed effort goalwards after cutting inside, but his shot whistled past the near post. Jed Wallace then received the ball from Smith and twisted and turned in an attempt to carve out an opening but his shot was blocked behind. Murray Wallace blasted over from a corner-kick, before Smith's nutmeg of Rooney sent away Leonard, with his attempt well saved by Hamer in the final action of the half.
Leonard very nearly charged down Hamer's attempted clearance as the second-half was just minutes old, with Duane Holmes having his shot blocked at the other end. Derby - adamant to play out from the back - were almost caught out by Leonard once more; his charging tackle letting Hamer know he was there.
Goalscorer Sibley then looked set to nudge The Rams into the lead with 57 minutes on the clock, but his effort went over Bialkowski's crossbar. With 71 minutes played, however, The Rams did put themselves in the ascendancy after Sibley latched on to a pass and slotted past the stopper into the far corner of the net.
That facilitated a move to two up front from Rowett, with both Bodvarsson and Tom Bradshaw entering the fray in place of Smith and Leonard, with Connor Mahoney and Jiri Skalak also both coming on with just under 10 minutes remaining, but with the game coming to a conclusion, Sibley's scuffed effort ended the game as a contest and sealed his hat-trick.
Bodvarsson's effort was judged to have crept over the line deep into stoppage-time, but The Lions could not find an equaliser, suffering defeat.
Millwall: Bialkowski, M. Wallace (Mahoney 81'), Hutchinson, Cooper, J. Wallace (Skalak 81'), Smith (Bodvarsson 74'), Ferguson, Romeo, Molumby, Leonard (Bradshaw 74'), Woods (Williams 86'). Subs not used: Steele, Brown, Mitchell, Muller.
Scorer: Smith 15', Bodvarsson 90+3'
Derby County: Hamer, Wisdom, Forsyth, Waghorn (Shinnie 76'), Lawrence, Clarke, Holmes (Knight 62'), Rooney (Martin 85'), Bogle (Davis 76'), Sibley, Bird (Evans 85'). Subs not used: Roos, Jozefzoon, Lowe, Whittaker.
Scorer: Sibley 26' 71' 90'
Booking: Waghorn, Sibley
Referee: Stephen Martin