Tottenham twice came from behind to claim a 2-2 draw on Mauricio Pochettino's return to St Mary's Stadium and remain ahead of Southampton in the race for UEFA Europa League qualification.
Southampton looked set to leapfrog Pochettino's new club in the Premier League table when Graziano Pelle headed his second goal of the game with 25 minutes remaining.
However, Spurs showed character to equalise through Nacer Chadli five minutes later and stay a point above Ronald Koeman's side.
Ryan Mason and Ben Davies - recalled to Tottenham's team together with fit-again skipper Hugo Lloris - were each guilty of errors as Southampton opened the scoring through Pelle shortly before the half-hour mark.
Yet the visitors drew level for the first time two minutes before the break when Erik Lamela converted a cross amid suspicions of handball.
Tottenham saw plenty of the ball early on, but the game's first meaningful chance did not arrive until the 25th minute, when Morgan Schneiderlin's cushioned volley from a James Ward-Prowse corner forced Lloris to dive to his left and pull off a fine save.
Lloris was left helpless four minutes later, however, as Tottenham gifted the lead to their opponents.
Mason slipped and played a pass back towards his own goal after a Southampton counter-attack had broken down. Davies was then caught out as he attempted to shield the ball, with the alert Pelle sticking out his left boot and prodding past Lloris.
An unmarked Steven Davis should have done better when side-footing wide from 15 yards in the 39th minute, and that miss was punished as an Eric Dier cross took a slight deflection and appeared to strike Lamela on the left arm to wrong-foot Southampton goalkeeper Kelvin Davis.
Having missed a presentable opportunity before to the interval, midfielder Davis failed to test Lloris on two further occasions inside the first nine minutes of the second half, dragging a shot wide from the edge of the box before missing the target once more after excellent work from Pelle.
Tottenham came close to taking the lead against the run of play when a Chadli cross deflected off Nathaniel Clyne and narrowly over the crossbar.
Ward-Prowse, who had come in for Dusan Tadic in Southampton's only change, was replaced by Shane Long after 62 minutes as the hosts sought a winner.
And the substitute made a swift impact, crossing for Pelle to capitalise on poor marking with a firm header into the top-left corner.
Tottenham dug deep to find another response, Chadli holding off Maya Yoshida and directing a low finish across Davis for his 10th Premier League goal of the season following Dier's slide-rule pass into the right channel.
After Spurs left-back Davies was forced off with an apparent shoulder injury, Southampton came closest to a winner - Jose Fonte seeing one header blocked by Federico Fazio and another fly just over - but Pochetino had reason to be content on his return to a club he claimed to "still love" prior to kick-off.
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