Nathan Dyer came off the bench to deny his former club victory as the Swans claimed a valuable point at Southampton.
After a goal-less first half, Morgan Schneiderlin opened the scoring after 64 minutes when he nodded home after Rickie Lambert headed down a cross into the box.
But just as the home crowd were sensing only a second league win of the campaign, up popped substitute Dyer.
Just 16 minutes after having replaced Wayne Routledge, Dyer capitalised on a defensive mix-up as he took possession off defender Jose Fonte after keeper Paulo Gazzaniga's pass to the Portuguese, and the former Saint raced on and fired into the net via the far post.
Both sides pushed for a winner, but they had to settle for a point in the end of a tense encounter.
The Swans remained unchanged from the starting XI that took to the field for the 1-1 home draw with Chelsea.
Chico Flores again missed out due to a dead leg sustained in the Capital One cup win over Liverpool, which meant Garry Monk continued to captain the side in defence alongside Ashley Williams.
Nathan Dyer was named on the bench as he returned to his former club while Danny Graham missed out with a back spasm, so Luke Moore was included among the substitutes.
Southampton boss Nigel Adkins handed highly-rated youngster Luke Shaw his first Premier League start at left-back in place of Danny Fox, who was among the substitutes, while Rickie Lambert was preferred to lead the line with Jay Rodriguez on the bench.
Paulo Gazzaniga, Nathaniel Clyne, Maya Yoshida, Morgan Schneiderlin, Jose Fonte, Rickie Lambert, Gaston Ramirez, Jack Cork, Adam Lallana (capt), Luke Shaw (Danny Fox, 72), Jason Puncheon.
Kelvin Davis, Jos Hooiveld, Steven Davis, Jay Rodriguez, James Ward-Prowse, Emmanuel Mayuka.
Gerhard Tremmel, Angel Rangel, Garry Monk (capt), Ashley Williams, Ben Davies, Leon Britton (Itay Shechter, 65), Ki Sung-Yueng, Jonathan de Guzman (Kemy Agustien, 86), Pablo Hernandez, Wayne Routledge (Nathan Dyer, 57), Michu.
David Cornell, Alan Tate
, Dwight Tiendalli, Luke Moore.
The game started at a good pace, with Pablo Hernandez and Wayne Routledge posing early threats while Gaston Ramirez fired over for the hosts in a lively opener on the south coast.
Captain Adam Lallana then tested Gerhard Tremmel after Rickie Lambert nodded down Nathaniel Clyne's cross before Ramirez curled an effort just wide of the far corner with the Tremmel at full stretch.
The Swans replied via Ki Sung-Yueng who, after a great bit of trickery, unleashed a thunderous effort which keeper Paulo Gazzaniga did well to dive across and palm out for a corner.
Back at the other end, Garry Monk timed his block perfectly to deny Jason Puncheon an effort after the Swans lost possession in their own half, then Ramirez fired another effort just to the left of the far post as the clocked ticked past the half-hour mark.
The home crowd were on their feet again soon after, as a well-worked free-kick found Jose Fonte, but when the defender's initial attempted cut-back was blocked back into his path, it took an excellent block from Ben Davies to deny the Portuguese from testing Tremmel in what proved the last real action of the half.
Half-time: Southampton 0 Swans 0
The Swans carved open the first opportunity of the half, with Jonathan de Guzman and Rangel linking up to set Hernandez down the right, and when he cut back to Routledge, the winger's effort just flew over the bar.
It was Routledge's last effort of the afternoon as he was replaced by former Saints winger Nathan Dyer after 57 minutes.
Just a minute later, the Swans were almost punished for a loose pass from Leon Britton, with Lambert passing inside to Ramirez, but Ki slid in to clear and rescue the Swans.
But the visitors couldn't hold out any longer as Lambert again headed a cross along goal and Morgan Schneiderlin controlled before nodding past Tremmel after 64 minutes.
Michael Laudrup replaced Britton with Itay Shechter immediately as the Swans looked to go in search of an equaliser.
And they got just that just seven minutes later through that man Dyer.
The Saints sent possession back to keeper Gazzaniga, and when he passed to Jose Fonte, the defender was dispossessed by Dyer, who then raced on and fired into the net via the far corner.
Lambert then went close to regaining the lead within minutes for the Saints with a header that whistled past the post from a corner.
Laudrup made his final change with four minutes to go as Kemy Agustien replaced de Guzman.
The Swans then went close to pinching victory as Agustien found Michu down the left flank, and it took a superb intervention from Fonte to stop the cross from reaching Shechter just yards out from goal.
It set up a very tense finish at St Mary's, but both sides were forced to share the points.