Premier League: Tottenham 1 Southampton 0
Tottenham have endured a disappointing start to the 2014-15 campaign – failing to build on back-to-back victories in their opening two fixtures.
In contrast, Southampton have defied the odds to find themselves among the English top flight's leading pack in the early part of the season under new coach Ronald Koeman.
However, Pochettino, who swapped St Mary's Stadium for White Hart Lane during the close-season, saw a first-half strike from Christian Eriksen reduce the gap between the sides to two points in north London on Sunday.
The Dane beat visiting goalkeeper Fraser Forster with a low strike into the bottom left-hand corner five minutes before the break, the goal ultimately proving enough to end Southampton's seven-match unbeaten run in all competitions.
Koeman's men did have a chance to preserve their impressive record six minutes from time, but Sadio Mane failed to sort his feet out in the six-yard box as a glorious opportunity to equalise went begging.
Although Tottenham made 10 alterations to the side that drew 1-1 with Besiktas in the UEFA Europa League on Thursday, both teams were unchanged from their last Premier League outings.
It was the hosts who applied the early pressure, but Southampton went closest to snatching an early lead – Mane's shot deflected wide by Kyle Naughton after a dangerous Graziano Pelle cross from the right.
Both goalkeepers remained unchallenged until the 25th minute, when Erik Lamela's effort from 20 yards was tipped wide by Forster with the ball looking destined for the bottom-right corner.
A reckless tackle from Ryan Bertrand saw Naughton requiring lengthy treatment on the half-hour mark. The challenge went unpunished but Naughton's match came to a premature end, with Eric Dier brought on in his place.
Forster did just enough to push an Eriksen strike wide of his left-hand post in the 36th minute, but he was helpless when the former Ajax man tried his luck with a shot to the keeper's right four minutes later.
Eriksen's driven effort from the edge of the penalty area fizzed just out of the reach of the England international, and Nacer Chadli then hit the post after being sent through on goal by Emmanuel Adebayor.
Hugo Lloris had to wait until first-half stoppage time to make his first meaningful save – the Frenchman diving to his left to gather a deflected Dusan Tadic free-kick.
Younes Kaboul got off with only a yellow card when he brought down Mane as the last man in the 52nd minute, before Forster spilled the ball from an Eriksen cross at the other end.
Lloris then had to be alert to keep out a vicious Victor Wanyama shot following an unconvincing clearance from captain Kaboul, but Tottenham felt they should have been awarded a penalty in the 75th minute when Adebayor appeared to be barged off the ball by Nathaniel Clyne, who received his first England call-up this week.
Referee Mike Jones waved away the home side's appeals, but it made no difference as Southampton – who saw Mane fluff his lines in the closing 10 minutes after Bertrand had played in an excellent cross from the left – failed to find a way through their former manager's defensive line.