Kenny Jackett admitted he is unsure when Damien McCrory will return from injury.
The Irishman underwent surgery after limping out of Pompey’s 4-1 victory against Fleetwood in September.
McCrory is still suffering pain from the setback and has since returned to his parent club Burton Albion.
Jackett is liaising with the Brewers but has not put a timescale on when the left-back will be available for selection.
The Blues boss said: ‘It’s a reoccurrence of his knee.
‘After his operation, he can’t quite get fit and it’s causing him problems.
‘He has gone back to his parent club to assess it.
‘I don’t know what they will say – they will speak to us and make a joint decision.
‘It’s a tough one and it might need sorting out further – we’re not quite sure yet.’
McCrory moved to Fratton Park on transfer deadline day until January.