Three first-half goals in five minutes condemned Millwall to a 3-0 defeat at Derby County on Saturday afternoon in the Sky Bet Championship at Pride Park.
Once again, The Lions competed and showed their Championship credentials, but switched off for a five-minute period that saw David Nugent (2) and Matej Vydra win the game for The Rams.
Lions boss Neil Harris opted to stick with the same starting XI from last Saturday's 2-1 victory over Middlesbrough, with the only change coming on the bench, as Fred Onyedinma returned to take the place of Kris Twardek.
Millwall had The Rams camped in their own penalty area for the first five minutes of the afternoon as a result of some smart passing play, but were unable to breach the last line of defence. In Derby's first chance of the game, Joe Ledley sliced wide.
On 15 minutes, The Lions could - and should - have taken the lead, but after Lee Gregory's pass set Steve Morison away, the latter's cross was unable to be turned home after Gregory's shot was cleared off the line by Curtis Davies and Aiden O'Brien's follow-up attempt was blasted over.
George Saville's outstanding block prevented Vydra from getting an effort in on goal three minutes later, but with 23 minutes on the clock, Derby took the lead as Nugent flicked home a corner-kick at the near post.
Two minutes later, a slack ball from Saville allowed Vydra to break clear and rifle home past Jordan Archer from around 20 yards out. In the space of just over 120 seconds, The Lions had gone from comfortably holding their own to chasing the game.
The damage was not done there, however, as on 28 minutes, a seemingly routine cross was not dealt with, allowing Nugent to ghost in and shoot past Archer for Derby's third.
Millwall could have had one back two minutes before the half-time break, but Shaun Hutchinson could only guide his header wide of Scott Carson's post. Further chances came and went, especially for Mahlon Romeo, whose deflected shot nearly crept into the top corner, but The Lions remained scoreless at the whistle.
The second-half was two minutes old when Millwall were unfortunate not to register on the scoresheet. Good hold-up play from Gregory allowed the ball to drop into the path of O'Brien, but his vicious effort was well tipped over by Carson.
Archer had to be at his best to palm away Andreas Weimann's strike on 50 minutes, but again it was Millwall who were making the better chances in front of goal, with Gregory just unable to connect with Jed Wallace's cross on the stretch.
Somehow, The Lions' first goal of the afternoon did not come on 54 minutes, as Carson produced a Christmas miracle to stop Gregory volleying home from a few yards out. Had Millwall taken their chances up to this point, they may well have found themselves level or better.
Just after the hour-mark Derby appeared to have scored a fourth goal, but the strike was ruled out for offside. A triple substitution by Harris occured shortly after, with Onyedinma, Shaun Williams and Tom Elliott coming on for Gregory, O'Brien and Wallace.
James Meredith sliced wide as the visitors still huffed and puffed in an attempt to get back into the game, whilst on 76 minutes, Morison shot wide - if it wasn't already evident that this was not Millwall's day, it surely was now.
Substitute Sam Winnall could have added a fourth for The Rams with nine minutes remaining, but his attempt was deflected wide for a corner-kick.
Derby County: Carson, Forsyth, Keogh, Baird, Johnson, Weimann (Thorne 81'), Vydra (Russell 71'), Nugent (Winnall 72'), Davies, Ledley, Huddlestone. Subs not used: Mitchell, Martin, Lawrence, Wisdom.
Scorer: Nugent 23' 28', Vydra 25'
Millwall: Archer, Meredith, Hutchinson, Gregory (Elliott 65'), Romeo, Wallace (Williams 66'), Tunnicliffe, Morison, O'Brien (Onyedinma 65'), Saville, Cooper. Subs not used: Martin, McLaughlin, Craig, Thompson.
Referee: Darren England