A goal from Republic of Ireland striker Michael Obafemi dealt a serious blow to Manchester United's Champions League ambitions.
The Southampton striker just turned 20 a week ago, and celebrated by salvaging a point for Southampton at Old Trafford.
In truth, it hadn't even started that brilliantly for United either, as they looked to crack the Premier League's top four.
Anthony Martial found the prone body of Alex McCarthy after a misplaced James Ward-Prowse ball allowed him through on goal.
Southampton took the lead with just 12-minutes played.
Paul Pogba's lackadaisical dwelling in possession was pounced upon by Danny Ings who fed Nathan Redmond.
The winger pinged a ball to the far post where Stuart Armstrong was waiting to fire past David de Gea.
A three-minute spell mid-way through the first half saw United turn the game in their favour.
Marcus Rashford found the net after a lay-off from Martial.
And the French forward made it 2-1, cutting inside from the left and shooting right-footed past McCarthy.
Southampton can count themselves lucky they weren't reduced to ten men before the break.
Oriel Romeu avoided censure entirely, despite replays showing his studs making contact with the leg of Mason Greenwood.
United failed to build on their lead in the second half, and instead it was Southampton who sensed there was still a point on offer.
Shane Long (for Che Adams), Will Smallbone (for Armstrong) and Obafemi (for Romeu) were all attack-minded second half introductions.
Ultimately, it would be the 87th minute introduction of Obafemi that counted for most.
A Nathan Redmond run and shot was tipped over by De Gea, resulting in a James Ward-Prowse corner.
Victor Lindelof failed to deal with Obafemi's movement, and he was able to get enough on Ward-Prowse's ball to direct the ball goalward and deny United all three points.