Charlton could still be without skipper Jason Pearce for Pompey’s visit to The Valley on Saturday.
The former Blues player hasn’t featured for the Addicks since the end of December because of and ankle injury.
And despite making the bench for Charlton’s 2-1 win at AFC Wimbledon on February 23, the 31-year-old failed to make the match-day squad for Saturday’s 1-1 draw at Doncaster Rovers.
Boss Lee Boyer confirmed the defender was still ‘hurting’ from the injury.
There’s every chance now that Pearce will not feature when his former employers travel up to the capital on Saturday (5.30pm kick off) when precious League One promotion points will be up for grabs.
Kenny Jackett’s side currently sit fourth in the table – five points behind second-placed Barnsley.
Meanwhile, the Addicks are fifth, a further five points adrift.
Speaking to Londonnewsonline.co.uk after Saturday's draw at the Keepmoat, Bowyer said: ‘His (Pearce’s) ankle was still hurting him so we said there is no point you just keep playing through this at the moment.
‘If there is anywhere we are strong at the moment it is that position – we’ve got Krystian Bielik who can fill in there and Anfernee Dijksteel.
‘We need to get him right for when we do need him.
‘He went for a scan on Friday morning and had another injection in the afternoon. We’re just trying to settle it down.
‘His ankle ain’t right. It’s too early to say, regarding an operation.
‘He has had some stuff put in there to loosen it up, because he is really stiff and tight at the front of his ankle.
‘Then he had another injection to try and take away the pain.
‘Hopefully that is going to work but we’ll know more in the next 48 hours.’
Former Fratton Park apprentice Pearce made 44 Championship appearances for Pompey during the 2010-11 season, following his return from a spell at Bournemouth.
That season he was named The News/Sports Mail player of the year, before moving to Leeds for an undisclosed fee in the summer of 2012.
The centre-half has played 21 games for Charlton this term and 75 in total since arriving from Wigan in August 2016.