They briefly levelled through Joe Aribo but were a man down from the 39th minute after captain Jack Stephens was sent off for pulling the hair of Marc Cucurella.
A team plagued by injuries and suspensions was unable to keep Enzo Maresca's Chelsea quiet and required Joe Lumley and Ryan Manning to keep the score down.
Here's how we rated every Southampton player's performance against the Blues, who now sit second in the Premier League after their win...
Southampton were thrashed 5-1 by ChelseaSouthampton were thrashed 5-1 by Chelsea (Image: Stuart Martin) Starters
Joe Lumley - 5.
Beaten at the near post from a corner for Chelsea's first before gifting them a second. Went on to concede three more but did make saves to deny Cole Palmer and Noni Madueke, preventing a cricket score.
James Bree - 5.
Came in for his first start of the season, replacing Yukinari Sugawara. Part of a makeshift Southampton defence which failed to adequately stop the Premier League's top goalscorers but carried himself fairly well.
James Bree started his first Premier League game of the season (Image: Andrew Matthews/PA) READ MORE: Bree on Chelsea: 'I think 5-1 at the end of the day flatters them a little bit'
Nathan Wood - 6.
Made his long-awaited Premier League debut in the absence of regular centre-backs. Gave a good account of himself despite the result. Completed 65 of 66 passes. Won all of his tackles and lost just one duel. Lost Jadon Sancho for Chelsea's fifth.
Jack Stephens - 3.
Played in a defence which shipped three goals inside 34 minutes before being shown a straight red card after a VAR check found he had pulled at Cucurella's hair. Let his teammates down when they were already depleted - really poor.
Jack Stephens has been SENT OFF FOR PULLING MARC CUCURELLA'S HAIR! 😱#PLonPrime #SOUCHE pic.twitter.com/XXgfZONCES
— Amazon Prime Video Sport (@primevideosport) December 4, 2024
Kyle Walker-Peters - 5.
Helped get Saints back on level terms by spinning Enzo Fernandes and providing the assist for Aribo. However, received a pass from Lumley while under pressure from Madueke, who pinched the ball and fed Nkunku for an easy goal. Not bad though.
Ryan Manning - 6.
Was Southampton's best player. Did fail to stop Madueke for Chelsea's third but also produced a last-ditch slide tackle which prevented the England winger from scoring a second from three yards out. Created two chances. Continues to impress in a poor Saints team.
Ryan Manning continues to impress in a struggling Saints teamRyan Manning continues to impress in a struggling Saints team (Image: Stuart Martin) Joe Aribo - 6.
Restored the good feeling at St Mary's temporarily when he tapped in from close range due to good positioning. Chipped in with important defensive actions and helped Saints maintain a threat on the break, bringing good energy throughout.
Mateus Fernandes - 5.
Was not allowed to be as free-flowing in attack due to Southampton's lack of options in midfield. Denied by a good save from Filip Jörgensen, who blocked his effort with his feet. Not a standout match for the Portuguese but no reason to worry.
Ryan Fraser - 5.
Played 62 minutes without having a real impact on things offensively or defensively, especially when compared to his role at Brighton. Dropped deeper following Stephen's red card before being replaced by Kamaldeen Sulemana, a more attacking option.
Ryan Fraser failed to impact the game against ChelseaRyan Fraser failed to impact the game against Chelsea (Image: Stuart Martin)
Adam Armstrong - 4.
His yellow card early in the second half was the most noteworthy moment of the game. Managed just 16 touches - with only two of those in the Chelsea box - before being replaced on 62 minutes. Fairly anonymous.
Cameron Archer - 6.
Really positive in attack. Showed endeavour by getting onto the ball and driving at the Chelsea defence to varying levels of success. Created a chance for himself by running from the halfway line but probably should have cut back for Fraser.
Axel Disasi blocks Cameron Archer's effortAxel Disasi blocks Cameron Archer's effort (Image: Stuart Martin) Substitutes
Kamaldeen Sulemana - 4.
Did little with his opportunity to impress Martin - again. He registered 15 touches and failed to complete any of his three dribbles. You wonder if and when it's going to work for the Ghanaian in a Saints shirt. Sam Amo-Ameyaw should probably get the chances.
Ben Brereton Diaz - 4.
Entered the field alongside Kamaldeen and ha no impact. Shook the hand of the supporter who entered the field of play - is that worth mentioning? Had seven touches as Saints looked to hit him, hoping the ball would stick up the field.
Summer signing Ben Brerton Diaz is yet to score for Southampton.Summer signing Ben Brerton Diaz is yet to score for Southampton. (Image: Stuart Martin) Yukinari Sugawara - 5.
Replaced Archer as Martin elected to bank up with 10 men. The plan did not work as Chelsea scored a further two goals. Was not really allowed to attack it seemed, given the situation of the game, which is the better side of his skillset.
Ronnie Edwards - N/A.
Came on for his Premier League debut when he replaced Bree. Completed all five of his passes. Could factor into Martin's plans on Saturday when Saints visit Aston Villa.
Charlier Taylor - N/A.
Replaced Fernandes, adding further defensive numbers for a hapless Southampton. Did little of note but his first feature in the squad since September.