Pochettino swapped the south coast for north London over the close-season and Southampton were thrown into a state of flux as star players Rickie Lambert, Adam Lallana, Dejan Lovren, Luke Shaw and Calum Chambers also sought pastures new.
But Southampton have rebuilt impressively under new boss Ronald Koeman and are enjoying a superb start to the current campaign.
Southampton currently sit second, five points better off than Tottenham, and it is a mark of the progress made under Koeman that the former Netherlands international fielded questions on the prospect of securing a top-four finish this term at his pre-match press conference.
The 51-year-old is cautious over the prospect of a surprise bid for UEFA Champions League qualification after four wins from six matches, but he believes bettering last season's excellent eighth-place finish under Pochettino is a realistic ambition.
Koeman said: "If we continue like this I think there is a possibility [of a top-four finish] but normally teams like Tottenham, like Man United - they will be up in the list because they have enough very good players.
"We try to do it in our way and if we keep the belief, keep the spirit, nothing is impossible.
"We had a lot of changes. We had good scouting in the club.
"We've brought good players in and maybe the challenge now is higher than last season.
"Maybe everybody was surprised with eighth position in the table last season but the people love how the team is doing everything to beat that."
Tottenham began the season with back-to-back London derby triumphs over West Ham and QPR, but have not tasted league victory since.
Thursday night's 1-1 UEFA Europa League draw against Besiktas meant the 3-1 League Cup win over Nottingham Forest the week before remains the club's solitary win in seven attempts across all competitions.
It means a three-point haul against his former club is of paramount importance to Pochettino, who is unsure over how he will be received by the visiting supporters on what he expects to be an emotional occasion on Sunday.
"I know it's football," he told reporters. "Now I am happy that they are happy at the beginning of the season and for me that is enough.
"But in football, sometimes you deserve the treatment you get, sometimes you don't deserve it. Some people say okay, some people say no. But this is just football.
"I'm happy Southampton are having a great season and at the end of it all, it's a game that we need to win the three points from and we need to fight with Southampton on Sunday.
"But it's emotional. Football is emotional and Sunday is emotional for us too."
Right-back Kyle Walker (hip) remains Tottenham's only absentee, while Koeman must assess defensive duo Maya Yoshida (ankle) and Florin Gardos (calf).
Southampton forward Jay Rodriguez and midfielder James Ward-Prowse are not due to return from respective knee and foot injuries until December.
