Millwall slipped to second successive away defeat as first-half goals from Damien McCrory and Nasser El Khayati sent Burton Albion top of the table in a game that saw The Lions finish with 10 men following the injury-time dismissal of Mark Beevers.
Having gone 2-0 down against the run of play courtesy of two clinical pieces of finishing in a seven-minute spell from McCrory (35mins) and El Khayati (42mins) before half-time, The Lions worked themselves right back into the game with Joe Martin's first goal for the club 15 minutes from time.
Despite throwing everything at the Brewers in the closing stages, Millwall had to play the final three minutes of injury-time a man down when Beevers, bppked earlier in the half for a foul, was shown a second yellow card after getting into a tangle following a goalmouth scramble.
It was as harsh a dismissal for the defender as defeat was for Neil Harris' side, who really deserved a share of the spoils in the first ever meeting between the two teams.
Harris made three changes to the team that beat Bury on Saturday with Martin returning from suspension to fill the left-back berth, Sid Nelson replacing Byron Webster, himself ruled out with a one-match ban, and striker Steve Morision partnering Aiden O'Brien up front having recovered from illness.
It was Burton, who smashed five goals past Colchester on Saturday, who carved off the first chance of the game on four minutes with a thumping shot from Tom Naylor that whistled past the upright.
However The Lions soon settled into their stride and created an opportunity of their own with nine minutes on the clock. Moments after Shaun Williams' 25-yard free-kick had been cleared by the home defence, Shaun Cummings lofted the ball back into the mix. Defender Beevers headed on to O'Brien, but the latter couldn't get enough purchase on the ball and directed his shot straight into the arms of keeper Jon McLaughlin.
Less than 60 seconds later a long diagonal ball from the back by Nelson picked out Morison, who was split between two defenders. Morison worked enough space to get in an effort on goal, only to see his dinked shot land on the roof of the net.
Millwall appealed for a penalty, or at least a freekick, but a strange decision saw a drop ball awarded just six yards out from the goalline after Nelson's header was virtually sat on by a Burton player. Morison was the Lions player to take the drop ball, but Burton cleared the danger.
O'Brien had the ball in the back of the net midway through the opening half, but was harshly penalised for handball in the build-up when the ball seemed to bounce off his arm, and to add insult to injury, was then booked.
George Saville had his name taken 10 minutes later for a foul on the left of the penalty area, and it proved a costly free-kick to concede with the ball played short to McCrory and he smashed an unstoppable shot into the roof of the net from just inside the box.
The goal really was against the run of play, but Millwall's response was positive and Morison was unlucky with a 39th-minute piledriver that was saved at full stretch by McLaughlin.
Harris' charges were attacking with purpose in search of an equaliser, but it was from a Lions corner that Burton broke swiftly and doubled their tally three minutes before the break. An incisive forward pass from Mark Duffy split the visiting defence and picked out El Khayati, who gave Archer no chance with an emphatic finish.
But for the brilliance of Archer, it could have been even worse for Millwall, with the keeper superbly parrying Naylor's goalbound shot and then using great athleticism denying John Mousinho and El Khayati in quick succession.
Manager Harris made two changes at the break replacing Saville and Ferguson with Ben Thompson and Lee Gregory and the move added fresh impetus to the visitors, who came out all guns blazing looking to get a foothold back in the game.
O'Brien sent a low drive a yard wide, Martin's inviting delivery dropped just beyond the reach of Morison and then Beevers headed wide from a Williams' corner as the Brewers were put under tremendous pressure.
Hard as The Lions tried, they were unable to turn that spell of pressure into a goal and instead it was El Khayati who nearly crafted a third goal for Burton, weaving his way into the danger zone and drilling an angled shot that was bravely blocked by Thompson.
Millwall did finally get the goal that their persistence and performance deserved with 15 minutes remaining when left-back Martin brought an almighty goalmouth scramble to an end by ramming the ball over the line from close range.
It was game on now, and with The Lions fans roaring their team on, Harris' men had the momentum to grab an equaliser.
Millwall had a huge shout for a penalty waved away on 77 minutes when O'Brien appeared to be hacked down, but again the decision went Burton's way.
They so nearly grabbed a leveller when, following another Williams' corner, the ball pinged around the penalty area before Onyedinma sent a stunning overhead kick agonisingly wide of the target.
However Millwall's hopes of gaining anything from the game were all but over when, following another attack by the visitors, Beevers ended up in the back of the net after he appeared to trip over the keeper. Unfortunately for Beevers - and to the disbelief of the away fans packed behind the goal - the Lions centre half was shown a second yellow card.
It was a hugely contentious decision and with time running out, Millwall just did not have that extra body to push on one last time and get the leveller that they so richly deserved.