And keeper Corey Addai has also departed after spending a section of pre-season with the Blues.
Danny Cowley was weighing up handing both players dealsm but the club have decided not progress matters on both fronts.
The News understands the decision is not a financial one, and both players would easily have fitted into the club’s playing budget.
Mingi arrived after leaving Charlton with the 20-year-old coming through the ranks at West Ham.
Giant 6ft 7in keeper Addai is a free agent, after being released by Championship outfit Barnsley this summer.
Both players would have gone into the category of the young players Cowley wants on the periphery of the Pompey squad.
Jayden Reid and Liam Vincent have both arrived this summer and fall into area, with the Blues head coach still on the hunt for young talent.
He said: ‘We haven’t got young players coming through so we’re looking for some who can support the team.
‘We want four I can really develop and work with.
‘They are really hard to find though, because the Premier League clubs have got them all and tend to stockpile them.
‘It’s a tough challenge because they tend to be in those Premier League clubs.
‘We’ll keep looking for the players we need though - and we’ll get there.’
Pompey have so far recruited eight players this summer.
Liam Vincent, Clark Robertson, Shaun Williams, Ryan Tunnicliffe, Kieron Freeman, Gavin Bazunu, Gassan Ahadme and Jayden Reid are the new faces to arrive to date.