The Blues boss believes his squad needs another seven players to be competitive in League One next season.
And he has revealed the exact areas of the squad which still need attention as he continues his overhaul.
Cowley has added eight signings to his options this summer, to give him a current squad of 20 players.
Liam Vincent, Clark Robertson, Shaun Williams, Ryan Tunnicliffe, Gavin Bazunu, Kieron Freeman, Gassan Ahadme and Jayden Reid make up the new additions to date.
Their arrivals have boosted numbers after 11 first-team players departed this summer, after failing to agree new terms.
The Pompey boss sees gaps for a new keeper and two further additions in each section of the pitch, with five weeks until the close of the summer transfer window.
Cowley said: ‘We need another five, six or seven players.
‘What do we need? Categorically, we’d like another keeper and we would like another left-back.
‘We would like to have four centre-halves.
‘You need four centre-halves and, at the moment without Paul Downing, we have two centre-halves.
‘So we would definitely like another centre-half.
‘We would definitely like two more in midfield. We would like a number six and probably a number eight.
‘Then we would like a 10 and a nine.’
Of Cowley’s existing squad, three of the players - Jayden Reid, Liam Vincent and Haji Mnoga – are seen as ones for the future, with loans being considered next season to continue their education.
The 42-year-old has made it clear he would like a total of four young players in that category, with no one making the transition from the academy to first-team set-up this summer.
So there is still a space available for someone to arrive who fits that bill, if a suitable emerging prospect can be found in the coming weeks.
Cowley added: ‘We’ve got four wingers at the moment and with Jayden it’s five.
‘With some of the young players though, it’s just a case of seeing how they develop in pre-season and then make a good decision about their playing pathway.
‘We’d like 22 first-team players and then three or four young ones. That would be the aim.
‘Then with the young ones you decide whether they have a loan or stay for their pathway.’
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