Paul Downing and Ellis Harrison are both set for an extended spell on the sidelines.
The Pompey duo both limped off injured during the recent Papa John’s Trophy defeat to Sutton at Fratton Park.
Downing has a hamstring problem, while a heavy challenge left Harrison nursing a badly swollen ankle.
And the duo join Clark Robertson in the treatment room, with the skipper still set to be out for a while.
Blues boss Danny Cowley said: “We’ve had the scan results back and they’ll be out for the foreseeable future – hopefully weeks rather than months.
"We’ve already lost one centre-half for the long-term, so to be without another in an area we’re light is disappointing."
“Paul is possibly slightly in front of Ellis. We’ll see how they come through the different stages of their rehab.
“We’ve already lost one centre-half for the long-term, so to be without another in an area we’re light is disappointing.
“They’re the cards we’ve been dealt with, however, and so we just have to find a way to deal with it.”
Pompey can call upon the services of Ronan Curtis again, however, with the Republic of Ireland international suspended for the weekend loss at Rotherham.
Cowley said: “It’s good to have him back – we missed his robustness and quality on Saturday. We’re pleased to be able to bring him back.”
🚜 Up next at Fratton Park#Pompey— Portsmouth FC (@Pompey) October 14, 2021