Pompey are targeting ‘high-level’ opposition to complete their summer friendly programme.
However, those fixtures won’t be finalised until after Pompey’s play-off fate is resolved.
Kenny Jackett’s men are booked in for six pre-season matches in the build-up to the 2019-20 campaign.
Kicking off against League of Ireland Premier Division side UCD on July 10, they include the traditional trip to the Hawks (July 13) and a visit to Crawley (July 27).
In addition, three fixtures are labelled as ‘Pompey XI’ outings, involving Bognor (July 16), Aldershot (July 23) and Woking (July 30).
However, there remains a vacancy for Saturday, July 20.
The Blues have also been known to fulfil a first-team game on the same midweek day as Pompey XI fixtures.
According to Mark Catlin, more friendlies will be announced – once the club know whether they will feature in League One or the Championship next term.
He said: ‘We are still working on a couple of potentially high-level opponents to fill that gap.
‘They will be away from Fratton Park, although I don't believe they will be abroad.
‘A lot will depend on the level we are at. If we end up in the Championship, you don’t want to be potentially playing one of your competitors, you could end up drawing them in a game a week later, that doesn’t work.
‘A few seasons ago we had a friendly lined-up against Cardiff, but had to cancel it because we then drew them in the EFL Cup, so that’s an example of the planning we have to put into it.
‘We need to find out what level we’ll be at before finalising those last few fixtures.
‘It could change.’
However, Fratton Park is out of bounds, with stadium and pitch work ruling out its use during the pre-season period.
The Blues are weighing up lodging a request with the Football League for their opening fixture of the 2019-20 season to be played away.