Millwall ended the Sky Bet Championship season with a fifth successive win at Swansea through Casper de Norre’s first goal in English football.
Belgian midfielder De Norre gave the Lions a 1-0 victory, sweeping home Danny McNamara’s 72nd-minute cross after Swansea winger Ronald had been caught in possession.
Millwall were also indebted to a penalty save from Matija Sarkic six minutes earlier, the Montenegro goalkeeper pushing away Matt Grimes’ kick that was too close to him.
Both sides played out the closing stages with 10 men as a largely tepid end-of-season affair burst into dramatic life.
Swansea substitute Jerry Yates and Millwall defender Japhet Tanganga were sent off five minutes from time after clashing angrily.
Victory took Millwall above Swansea in the final Championship standings, the Lions climbing to 13th with their Welsh hosts one place and two points worse off.
Both sides had been in good form with Swansea taking 10 points from 12, their best run since four successive wins through September and October, while Millwall had banished their own relegation concerns.
The Lions had the first opening as Swansea allowed Zian Flemming’s long throw to bounce in their penalty area.
The ball found its way through to Tom Bradshaw, but his goalbound attempt was snuffed out by the alert Josh Key.
Swansea gradually established command and Ronald skied over at the far post with the goal gaping.
Key’s powerful burst ended in half-hearted penalty appeals and Millwall survived again just before the half-hour mark.
Ollie Cooper cut infield to deliver a dangerous cross that Jamie Paterson, out of contract in the summer and possibly playing his final Swansea game, diverted over.
Charlie Patino slipped Ronald through for another sight of goal, but this time the Brazilian was stopped by the onrushing Sarkic.
Millwall had not threatened until the early exchanges but two minutes before the break Ryan Longman strode through the middle to warm the hands of Carl Rushworth.
The visitors went close again after the restart after McNamara was picked out by Romain Esse and the full-back’s curling effort was deflected just wide of the far post.
Jake Cooper sent a header into the gloves of Rushworth as Millwall raised the tempo and McNamara and Longman were thwarted by last-ditch defending.
Swansea were awarded a penalty when Paterson’s through ball ended with Ronald tripped by Cooper.
Sarkic dived to his right to deny Grimes and Paterson sent the rebound over to keep the game goalless.
Millwall made the most of that break when Ronald was caught showboating and McNamara pounced to set up a delighted De Noore, who celebrated wildly in front of the travelling fans.
Yates was sent on from the bench to restore matters, but he spent only 11 minutes on the field after an unseemly spat with Tanganga saw their campaigns end prematurely.
