Damien McCrory is not expected to feature for Pompey this month.
And Blues boss Kenny Jackett is uncertain whether the left-back will be available for selection beyond that as his injury problems continue.
The 27-year-old has been sidelined since mid-September after damaging his knee against Fleetwood.
Despite a subsequent operation, he has continued to suffer pain and returned to parent club Burton for attention.
As it stands, McCrory has made just three appearances since his deadline-day arrival from the Championship club.
With his loan spell scheduled to expire in January, time is ticking down on whether he will feature for Pompey again.
And Jackett revealed the full-back is no closer to a return to playing action.
He said: ‘We don’t know any more about Damien.
‘He has gone back there (to Burton), he is being assessed and will need a period after this operation to rehab.
‘It’s not something he is going to make a quick return from, I don’t think.
‘Obviously, time is running out for us anyway for his return, but we are certainly not expecting it this month – and after that it depends how the knee settles down.
‘The remainder of November will decide whether we can make up some time and get him back in December.
‘We’ll see, it very much depends on them (Burton), but at the moment he’s not close to a return.’
It represents continued misfortune for Jackett in the left-back slot.
Tareiq Holmes-Dennis was recruited on loan from Huddersfield to replace Enda Stevens and caught the eye during pre-season.
However, he sustained knee-ligament damage 39 minutes into the League One opener against Rochdale.
Despite being on a season-long loan, Holmes-Dennis is not expected to play for Pompey again this campaign as he continues his rehab at the John Smith’s Stadium.
McCrory was recruited as the 22-year-old’s replacement – only to also be struck down by knee problems.
Dion Donohue has chiefly stepped in as the Blues’ left-back, although Jackett regards the August recruit as primarily a midfielder.
Regardless, the former Chesterfield man has started nine matches at left-back for the club.
Brandon Haunstrup has also featured, replacing Donohue in last weekend’s FA Cup defeat at Luton for his sixth Pompey start under Jackett.