SWANSEA played for 85 minutes with 10 men at The Den on Saturday evening but came from a goal down to hand Millwall a third successive league defeat.
Millwall went 1-0 up in the 62nd minute through Murray Wallace, but substitute Jefferson Montero set up goals for Kyle Naughton and Oli McBurnie in the last 14 minutes.
Swansea were a man down from the fifth minute when Courtney Baker-Richardson was given a straight red card for a tackle on James Meredith.
After Jed Wallace went closest to scoring in the first half, defender Wallace gave a dominant Millwall the lead when he headed in.
But Naughton levelled with a low shot from the edge of the box and McBurnie finished off a rapid counter-attack with five minutes left.
Both sides hit the woodwork late on, substitute Tom Elliott's header off the crossbar Millwall's last chance.
First half – Swans down to 10 but Lions struggle for cutting edge
Millwall boss Neil Harris made two changes from the side that started in the 3-2 defeat of Plymouth in the EFL Cup in midweek.
Jordan Archer wasn't in the match-day 18, so Amos made his league debut for the Lions. He could do little about either goal. Ryan Leonard – who completed his move from Sheffield United at 4.57pm on Friday, three minutes before the deadline – wasn't signed in time for the game.
Baker-Richardson would have a difficult case to make to argue his league debut shouldn't have ended so early. After losing possession he went in late and high on Meredith, who was lucky his left leg was slightly raised off the ground.
Swansea also lost their captain Leroy Fer to injury before the break. Naughton came on and the Swans had five across the back when Millwall had the ball.
That was for the majority of the first half, but the hosts only created one clear-cut chance. In the 24th minute Steve Morison headed the ball down to Wallace, who was through on Erwin Mulder. Wallace could even have taken the ball on, but shot instead and skewed wide when he at least should have hit the target.
Millwall fans chanted "England" at their opponents and Swansea fans retorted with "Football's coming home". They were encouraged by the performance of their team. Swansea were dangerous on the ball and moved it quickly, and Mahlon Romeo had to scamper back and across the pitch in 27th minute to put pressure on Daniel James, who shot wide after a break from a corner.
The Swans read Millwall's intentions well and defended long diagonal balls towards Morison, that one Wallace chance aside.
Second half – Millwall somehow lose it
Millwall had well over 60 per cent possession in the first half and continued that kind of dominance after the break, but so too did their lack of precision in the attacking third persist.
Aiden O'Brien ran a long distance with the ball in the 55th minute but then shot over, before Wallace fired wide from outside the box.
The sense was Millwall needed to do something different, and in the 59th minute Jiri Skalak came on for O'Brien.
Skalak certainly made an immediate impact, first seeing a cross cleared before he played Wallace down the right and the winger earned a corner. Swansea had been forewarned, but it is one thing knowing what is likely to happen and another trying to defend it. Williams clipped the corner to the back post, Jake Cooper headed it back across goal, and centre-back Wallace twisted to glance the ball home.
Millwall went close to a second goal with 20 minutes left and it was Skalak again involved when he crossed from the right and Ryan Tunnicliffe just missed making a connection at the back post.
Swansea hadn't had a shot on target until Montero turned away from Romeo on the left and found Naughton just outside the box. He quickly shifted the ball to his right foot before firing a low shot past Amos into the bottom left corner.
With nine minutes left Wallace found Skalak in the box and he aimed for the far top corner but his effort went wide.
In the 85th minute, Romeo was caught offside deep in Swansea's half. The visitors took the free-kick quickly and Montero played a one-two with Bersant Celina before advancing into the left side of the box and squaring for McBurnie to tap in.
Millwall brought on Elliott and Tom Bradshaw for full-backs Romeo and Meredith late on.
Tom Carroll struck a shot off the post in injury-time, before, with the last play of the game, Skalak crossed for Elliott whose header came down off the crossbar and into Mulder's clutches.
Image: Millwall FC