The Swans suffered their second defeat of the Barclays Premier League campaign following a 3-1 loss at Southampton.
Despite Gylfi Sigurdsson's late goal from the penalty spot, it proved a disappointing afternoon for Garry Monk's side at St. Mary's as the hosts claimed victory courtesy of goals from Virgil Van Dijk, Sadio Mane and Dusan Tadic.
Van Dijk opened the scoring for the Saints on 11 minutes as he headed home at the near post from James Ward-Prowse's in-swinging corner.
Mane then doubled the hosts' advantage shortly after the break with a low finish past Lukasz Fabianski before Tadic saw an effort from an acute angle deflect into the net off Ki Sung-Yueng.
After the Swans were awarded a penalty for Jose Fonte's foul on Neil Taylor, Sigurdsson kept his cool to pull one back for the visitors on 84 minutes.
The Swans rallied in the closing stages as Andre Ayew went close to pulling a second goal back for Monk's men with a well-timed header, but it proved all too late for the away side.
The Swans made one to the starting XI from last week's league stalemate with Everton.
Garry Monk, who saw his side lose to Hull City in the Capital One Cup in midweek, brought Ki Sung-Yueng back into his plans as the South Korean made his first start since the opening day of the season while Jefferson Montero moved to the bench.
Jack Cork made his first appearance against his former club having joined the Swans in January, while Jonjo Shelvey - the scorer of the only goal in the victory at St Mary's seven months ago - joined him in midfield.
Maarten Stekelenburg, Cedric Soares, Jose Fonte (capt), Steven Davis (Oriol Romeu, 62), Sadio Mane (Juanmi, 86), Dusan Tadic (Jay Rodriguez, 74), Victor Wanyama, James Ward-Prowse, Virgil Van Dijk, Graziano Pelle, Ryan Bertrand.
Kelvin Davis, Maya Yoshida, Shane Long, Cuco Martina.
Lukasz Fabianski, Kyle Naughton, Federico Fernandez, Ashley Williams (capt), Neil Taylor, Jack Cork (Jefferson Montero, HT), Ki Sung-Yueng, Jonjo Shelvey (Leon Britton, 79), Gylfi Sigurdsson, Andre Ayew, Bafe Gomis (Eder, HT).
Kristoffer Nordfeldt, Angel Rangel, Kyle Bartley, Wayne Routledge.
At a sun-drenched St. Mary's, Jonjo Shelvey was the first to test the reactions of opposition goalkeeper Maarten Stekelenburg with a powerful strike from 20 yards. The Saints stopper palmed Shelvey's fizzing effort straight into the path of Ki Sung-Yueng, but the South Korea captain couldn't keep his effort down.
At the other end, meanwhile, Sadio Mane was presented a fantastic opportunity to open the scoring when the ball fell kindly to him in the box, only to drag his shot narrowly wide of the post.
But the Saints took the lead just moments later when Virgil Van Dijk met James Ward-Prowse's corner with a crashing header in at the near post on ten minutes.
The Swans were struggling to find their usual fluency, with the hosts restricting Garry Monk's side to efforts from distance as Shelvey rifled over the bar midway through the first period, before Ki saw a driven effort saved down low by Stekelenburg.
HALF-TIME: Southampton 1 Swans 0
In an effort to find a way back into the game, the Swans made two changes at the midway point as Jack Cork and Bafe Gomis made way for Jefferson Montero and Eder.
But it was the Saints who doubled their advantage eight minutes into the restart as Dusan Tadic's strike from an acute angle deflected off Ki and over the head of Lukasz Fabianski.
Mane, who had proven a constant threat for the hosts throughout the afternoon, then made it 3-0 to Southampton on the hour-mark with a low finish from 12 yards.
The Saints were proving clinical in front of goal, but they were denied a fourth by Fabianski, who got down well to save Van Dijk's dipping free-kick, before the Polish international was called into action again to parry away Graziano Pelle's glancing header at the near post.
The Swans then went close to pulling one back following a neat move by the visitors, but Shelvey saw his effort on goal well blocked by Jose Fonte after the English midfielder was teed up inside the area by Neil Taylor.
With just under ten minutes left on the clock, the Swans were awarded a penalty for a Fonte foul on Taylor, which Sigurdsson calmly dispatched from the spot.
Buoyed by their 84th-minute goal, Andre Ayew then had a chance to pull a second goal back for the visitors when he rose high in the box to meet Montero's inviting cross, but the Ghanaian headed straight into the arms of Stekelenburg.
But the late rally proved too little, too late for the Swans, who suffer their second defeat of the season.