JED Wallace was sent off and Lee Gregory hit the post with the last kick of the game as Marvin Sordell scored the winning goal to give Burton Albion all three points at The Den.
Wallace was given a straight red card 13 minutes into the second half for a foul on left-back Tom Flanagan before Burton took the lead in the 70th minute through former Charlton striker Sordell.
Aiden O’Brien and then Wallace had gone closest for Millwall at the end of a very poor first half in which Burton barely posed any threat, save for a cross from Lloyd Dyer that James Meredith cleared.
A man down, Millwall failed to really put the Burton defence under proper sustained pressure as they chased an equaliser.
This fixture had offered Millwall a chance to put more distance between themselves and the bottom three, but instead the home side produced one of their poorest displays of the season as Burton scored from their only shot on target.
It was the visitors who came close to adding a second when Dyer, who was part of such an impotent attack in the first half, shot just wide of Jordan Archer's far post.
In the very last minute of added time, substitute Fred Onyedinma ran through on Stephen Bywater, the ball breaking off the goalkeeper to Gregory, who just failed to steer his effort inside the near post.
It was a first win at The Den for Burton, though these clubs’ histories didn’t collide until the 2015-16 season when Burton won at home and then O’Brien and Gregory scored in a 2-0 win in the return fixture.
Those two players were back in the Millwall side today, along with Steve Morison. With Jake Cooper suspended, Tony Craig, wearing the captain’s armband, started his first league game of the season.
Craig and the rest of the back four had so little to do in the opening half and it always looked like it would take an error to let in a side that had only scored nine league goals this season before kick-off, only Birmingham with a worse record.
Burton had also conceded more than any other club, but that wasn’t really evident as Millwall struggled to break them down, more to do with their own slack play than any defensive excellence from the Brewers.
Burton’s full-backs in a narrow back four rarely ventured over the halfway line meaning there was little support for Dyer and Sean Scannell, who saw so little of the ball. Worse, Burton’s front three hardly seemed bothered at times, Sordell failing to chase a ball that he could have kept from going out of play at one point in the first half.
Referee Tony Harrington didn’t help the frustrated mood in the stadium when he awarded a free-kick to Burton when it seemed obvious that Ryan Tunnicliffe was the player that had been fouled.
Neil Harris and Nigel Clough were both having words with the fourth official as half-time approached, both feeling decisions were going against their sides.
Any flair was being provided by Millwall. Just before the break Morison crossed to Wallace who connected first-time for a shot on goal that was off-target, the ball coming at O’Brien too quickly to give him time to adjust his feet.
O’Brien then crossed to Wallace whose flick was deflected out for a corner that came to nothing.
Burton’s front players looked a little livelier after the break as a Conor McLaughlin slip let Dyer away in the box, but Craig was there to cut out the cross.
Burton were playing marginally better since the break, though that wasn’t saying a whole lot, but their chances of winning were more than marginally increased when Wallace was shown red for sliding in on Flanagan. Harris almost immediately responded by sending on Ben Thompson for his first league action since April.
Tom Elliott was part of the double substitution, O’Brien and Morison going off. Referee Harrington angered the home fans more by pulling Harris aside for a talking-to after the Millwall boss and Flanagan exchanged words near the touchline.
It got worse moments later when Burton scored for just the second time on the road in the league this season, their first away in the Championship in seven games, Sordell – after Matty Palmer’s shot had fallen to him – digging the ball out from under his feet to fire home from close range despite McLaughlin’s effort to block on the line.
Thompson was one of three in midfield now for the Lions and he picked out the run of Elliott who found Gregory in the box, but the striker couldn’t twist into a shooting position and Burton cleared.
Onyedinma came on for Meredith with four minutes left and almost made that decisive late contribution as Gregory's curled effort smacked off the woodwork. Instead, Millwall have much to contemplate during the international break.
Image: Millwall FC