And the Blues’ head coach has urged supporters not to panic over the relative quiet when it comes to new arrivals.
Non-league youngster Liam Vincent is the only new face so far, while Jack Whatmough, Ryan Williams and Ben Close have all departed for League One rivals.
MK Dons have landed Swindon starlet Scott Twine, who was a name on Cowley’s list of targets this summer.
But Cowley explained it’s his attention to detail over signings he feels can improve the team, which is the dominant factor behind a lack of significant movement so far.
He said: ‘I totally understand their frustrations and also some nervousness and apprehension.
‘There always is when there’s a big turnover - and this is a huge turnover of our playing squad. Let’s not hide from that. We know how much we have to do.
‘As a club we’ve spent four years trying to get out of this division unsuccessfully.
‘We now have the chance to improve the squad and maybe a new game idea and new way of working.
‘I’ve been a football supporter and know how frustrating it can be. West Ham were never at the front of the queue for signings, so I know how it is.
‘I understand there’s a level of frustration, but that frustration should be towards me.
‘Really, the way we work, it takes time.
‘It is quite methodical and very process-oriented. There is a lot of stages we have to get through to get the right players.
‘Really, I’m just particularly fussy. That is the truth of it.
‘I won’t sign players for the sake of signing them and I only make change if I can get significant gain.
‘So I’m going to try to put a squad together which gives us significant gains.’
Pompey have been linked with moves for the likes of Jayden Stockley and Joe Morrell in recent days, but Cowley is staying coy on specific names.
But the head coach believes his recruitment record over a long period of time should offer assurances to supporters.
Cowley added: ‘I can’t speak about specific names and I apologise for that because I wish I could.
‘I’d be frustrated if I was a fan and I heard, but hopefully they can understand why I can’t.
‘I think we’ve done pretty well in recruitment over the years and it’s a huge part of why we’ve had the promotions we’ve had.
‘I do think football rewards people who recruit well, but it’s a game of poker and we don’t want to show our hand.’
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