Former Holland player Poortvliet has now been named as head coach in what the club has described as a 'new continental set-up'.
Poortvliet, who has previously had spells in charge of Den Bosch, Roosendaal and Stormvogels Telstar in his homeland, will be joined by fellow Dutch coach Matt Wotte.
Southampton's new coaching programme which will also heavily involve reserve team boss Stewart Henderson and youth team coach Dave Hockaday
Chairman Michael Wilde told the club's official website: "We are extremely grateful for Nigel's contribution. He came to the club at a time of crisis and through his hard work and commitment we were able to avoid relegation on the last day.
"However, the board have been looking closely at the situation on the playing side of the club whereby we are inevitably going to have to depend to a large extent on the quality of our youngsters in the academy and the reserve team.
"Our view on that was we would need to adopt a European-style coaching system comprising head coach, with the objective of linking the academy to the first team.
"The board believe this will create opportunities for our younger players, which might not occur within the traditional English management structure."
