The Blues keeper will be absent for the Shrews’ trip to Fratton Park as he is still sidelined with an ankle injury.
Bass picked up his knock in Kenny Jackett’s side’s penalty shootout victory at Stevenage in the Carabao Cup last month.
The academy graduate missed Tuesday night’s 2-0 victory over Colchester in the EFL Trophy.
Craig MacGillivray lined-up between the posts, while Duncan Turnbull featured in his first Pompey squad on the bench.
And it will be the same situation against Shrewsbury, with Bass still being troubled by bad bruising on his ankle.
The Blues are hopeful he’ll be back training at the start of next week.
Bass is the only injury concern for Jackett, however, and has a full complement of outfield players to select from.
Jack Whatmough’s vying to keep his spot in central defence alongside Sean Raggett, after replacing Paul Downing against Colchester.
Jackett also has to decide whether to stick with Gareth Evans in the number-10 role or bring in Andy Cannon.
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