Leeds United's Patrick Bamford and Tyler Roberts scored late on to spoil the party for Southampton fans as the visitors claimed a 2-0 victory in the Premier League match played in front of 8,000 supporters on Tuesday.
The Saints fans marched back into St Mary's Stadium full of enthusiasm after relaxed COVID-19 restrictions, creating an atmosphere more akin to the opening day of the season rather than the last home game of the campaign for their side.
But after a poor first half from Leeds, Bamford broke the deadlock in the 73rd minute when he beat the offside trap from Rodrigo's pass and steered the ball through the legs of goalkeeper Alex McCarthy.
Leeds scored their second in added time as their quick break caught Southampton without numbers in defence and Roberts scored his first goal of the season.
Leeds climb to eighth place on 56 points from 37 games and have ensured a top-half finish on their return to the Premier League, while Southampton stay in 14th with 43 points.
Saints' James Ward-Prowse struck the frame of the goal with a wicked, dipping 30-yard free-kick early in the second half before Leeds' first shot on target from Raphinha forced an excellent fingertip save from McCarthy.
Bamford should have put the Yorkshire side in front when he ghosted in behind the home defence and was left with McCarthy to beat, but the keeper forced him wide. The striker made up for that error with his opener, his 16th league goal of the season.