Kenny Jackett is adamant Conor Chaplin will not be allowed to leave Pompey unless a replacement can swiftly be recruited.
Coventry are comfortably in pole position to land the 21-year-old, with Bristol Rovers and Barnsley also declaring their interest.
While Pompey negotiate, Jackett acknowledges an urgency to bring in a striking alternative.
The transfer window closes on August 9, with free transfer and loan deals allowed to be secured until August 31.
Jackett is determined he won’t weaken his squad in order to strengthen League One rivals.
And he has threatened to cancel any potential Chaplin exit should he not have time to bring in better players.
The Blues boss said: ‘It’s not so much about the fee, it’s about strengthening the squad.
‘I am not going to weaken our team, I am not going to weaken our squad at this period.
‘If I can turn the situation into a positive for Portsmouth, then yes I will entertain it. But unless it turns into a positive for us where we get player or players to make us stronger then nothing is going to happen.
‘Considering quite a small fee and then just starting to look around is not going to be the case – there has to be somebody on the way that I feel improves us.
‘Are we looking for replacements? Yes, of course. Are we looking to improve the squad? Yes, no doubt.
‘But, similarly, I am realistic enough to know what the market is like at the moment.
‘If you phone up a competitor about a player it’s a very difficult conversation, we are not just going to step out of the way and improve someone and weaken ourselves.’
Another consideration is Chaplin’s contract, which ends in the summer of 2019.
Although the club are entitled to compensation should the striker – who is aged below 24 – walk away upon its expiry.
He added: ‘With Naismith we couldn’t ever quite get in control of that situation.
‘If a player is aged more than 24 at the end of the season then you have a decision to make contractually. You have to assess how much you are going to get out of that player for that last year.
‘In Conor’s case, he would still be under 24 at the end of the season and we would be in a tribunal situation.
‘We don’t want it to get to that, though. I would want players to be happy here and feel like they have a chance and an opportunity.
‘Even so, the bottom line is looking after the club.’