The game's key moment arrived when Mohammed Salisu fouled Son Heung-min, earning a red card and conceding a penaltySouthampton put on a show of resilience in holding Tottenham to a draw despite playing with 10 men for over 50 minutes at St Mary's.
Ralph Hasenhuttl's side started admirably when James Ward-Prowse cut across a bouncing ball to volley a swerving shot past Hugo Lloris for a superb opener.
But Saints looked to have undone their fine work when Mohammed Salisu fouled Son Heung-min in the box to earn a second booking in 12 first-half minutes and allow Harry Kane to score from the penalty spot.
Spurs twice had the ball in the net after the break, with Kane seeing a strike ruled out by VAR for a narrow offside and Southampton goalkeeper Fraser Forster spared own-goal blushes when it was judged he was fouled by Matt Doherty.
Tottenham may feel aggrieved by the decision on Forster's foul, but in truth they did not do enough after the break to pull and stretch a patched-up Saints back four, who repeatedly limited the visitors to crosses from wide areas.
The point means Spurs sit sixth in the table and Antonio Conte has become the first manager in the club's history to remain unbeaten in his first seven league games.
But he expected more after Salisu's red card and said his side "have to be disappointed".
Hasenhuttl, on the other hand, punched the air on the final whistle and said there was "no chance to be more proud than today".
Conte's record, Southampton's resolve
A foul was given against Matt Doherty when Forster - who made 10 saves on the day - turned the ball into his own netConte has now overseen four Tottenham wins and three draws in the league, and the likes of Pierre Emile-Hojbjerg explained before kick-off that the boss has called on players to raise their game technically, physically and in how they live as professionals away from the training ground.
Their effort could not be questioned in the second half at St Mary's, with Doherty being denied by Forster, Son seeing a header held, and substitute Bryan Gil having a stinging shot tipped over in injury time.
If anything, Spurs simply took too long to build momentum with their one-man advantage, and Southampton - beaten only by Wolves at home in the league this season - ground out a point to move to 13th in the table.
Hasenhuttl made six changes from the Boxing Day win at West Ham and his side's grit and resilience in the second period was typified by Kyle Walker-Peters, who leapt to glance a header away from the lurking Kane before immediately taking a Ben Davies shot flush in the face.
Spurs saw 53% of first-half possession, registering four shots. Those stats rose to 76% and 18 attempts in the second period - pointing to the significance of Salisu's dismissal.
The Ghanaian defender had appeared on edge in the first half, recording four fouls in 39 minutes as Southampton looked to play high up the pitch and harass Spurs into errors. His dismissal was Southampton's 11th since Hasenhuttl took charge in 2018, with only Arsenal having a higher tally, 13, in the same time frame.
The sharp Kane lashed his penalty high into the net and later came incredibly close to staying onside before applying a finish to a Harry Winks pass six minutes after the break.
But with the likes of the impressive Ward-Prowse winning all of his duels on the day, Southampton kept a solid shape to force Spurs wide. Conte's side delivered 28 second-half crosses compared with three in the first 45 minutes and had little to show for their approach.
And Southampton could have won it in injury time when Armando Broja robbed Tottenham defender Eric Dier before firing over, sparing Spurs further frustration on a day when they could have taken more.
Player of the match
Ward-ProwseJames Ward-Prowse
Line-ups
Southampton
Formation 5-3-2
44Forster
2Walker-Peters43Valery35Bednarek22Salisu15Perraud
17S Armstrong27Diallo8Ward-Prowse
7Long9A Armstrong
44Forster2Walker-PetersBooked at 13mins43Valery35Bednarek22SalisuBooked at 39mins15Perraud17S Armstrong27Diallo8Ward-Prowse7LongSubstituted forBrojaat 71'minutes9A ArmstrongBooked at 51minsSubstituted forRedmondat 83'minutesSubstitutes
6Romeu11Redmond13Caballero16Small18Broja23Tella24Elyounoussi32Walcott38SimeuTottenham
Formation 3-4-2-1
1Lloris
6D Sánchez15Dier33Davies
12Emerson Royal8Winks5Højbjerg3Reguilón
20Alli7Son Heung-Min
10Kane
1Lloris6D Sánchez15Dier33Davies12Emerson RoyalSubstituted forGilat 77'minutes8WinksBooked at 69mins5Højbjerg3ReguilónBooked at 45minsSubstituted forDohertyat 45'minutes20AlliSubstituted forLucas Mouraat 62'minutes7Son Heung-Min10KaneSubstitutes
2Doherty11Gil14Rodon22Gollini25Tanganga27Lucas Moura28Ndombele29Skipp42WhiteLive Text
Match ends, Southampton 1, Tottenham Hotspur 1.
Second Half ends, Southampton 1, Tottenham Hotspur 1.
Attempt blocked. Davinson Sánchez (Tottenham Hotspur) with an attempt from the centre of the box is blocked. Assisted by Son Heung-Min with a cross.
Corner, Tottenham Hotspur. Conceded by Jan Bednarek.
Corner, Tottenham Hotspur. Conceded by Fraser Forster.
Attempt saved. Bryan Gil (Tottenham Hotspur) left footed shot from the centre of the box is saved in the top centre of the goal. Assisted by Matt Doherty.
Attempt missed. Harry Kane (Tottenham Hotspur) header from the left side of the six yard box is close, but misses to the left. Assisted by Harry Winks with a cross.
Attempt blocked. Pierre-Emile Højbjerg (Tottenham Hotspur) right footed shot from outside the box is blocked.
Corner, Southampton. Conceded by Davinson Sánchez.
Attempt blocked. Armando Broja (Southampton) right footed shot from the right side of the box is blocked.
Attempt saved. Son Heung-Min (Tottenham Hotspur) header from the centre of the box is saved in the top left corner. Assisted by Harry Winks with a cross.
Attempt saved. Lucas Moura (Tottenham Hotspur) right footed shot from the right side of the six yard box is saved in the centre of the goal. Assisted by Matt Doherty with a through ball.
Attempt saved. Lucas Moura (Tottenham Hotspur) right footed shot from outside the box is saved in the centre of the goal. Assisted by Eric Dier.
Attempt blocked. Ben Davies (Tottenham Hotspur) left footed shot from outside the box is blocked.
Substitution, Southampton. Nathan Redmond replaces Adam Armstrong.
Offside, Tottenham Hotspur. Pierre-Emile Højbjerg tries a through ball, but Harry Kane is caught offside.
Attempt saved. Son Heung-Min (Tottenham Hotspur) header from the centre of the box is saved in the top centre of the goal. Assisted by Bryan Gil with a cross.
Attempt saved. Lucas Moura (Tottenham Hotspur) header from the centre of the box is saved in the bottom right corner. Assisted by Matt Doherty with a cross.
Substitution, Tottenham Hotspur. Bryan Gil replaces Emerson Royal.
Attempt missed. Matt Doherty (Tottenham Hotspur) right footed shot from the centre of the box is high and wide to the right. Assisted by Harry Winks with a through ball.
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