Matt Clarke is expected to miss Pompey’s League One kick off.
The central defender was forced off with a groin problem after 16 minutes of last weekend’s friendly at Hawks.
At this stage it is unclear whether the issue is related to the groin injury which grounded him last summer.
Regardless, the club do not anticipate Clarke being available for the August 5 curtain-raiser against Rochdale.
It represents a massive blow to the Blues’ preparations, with the 20-year-old having forged an outstanding central defensive partnership with Christian Burgess.