New Pompey recruit James Bolton is expected to be sidelined for up to a fortnight.
The former Shrewsbury man missed Saturday’s 2-1 victory over the Hawks with a groin injury.
In his absence, Anton Walkes stepped in at right-back, with Christian Burgess taking over as a substitute with 17 minutes remaining.
Yet Bolton has been earmarked as Nathan Thompson’s long-term replacement – and his injury set-back represents a blow.
Certainly he is expected to miss forthcoming friendlies at the Rocks (July 16) and Stevenage (July 20) at the very least.
Ross McCrorie was also an absentee at Westleigh Park, having been handed permission to return to Glasgow for the weekend.
Wigan target Jamal Lowe was another missing face, despite named on the team sheet, with Jackett explaining he had been given leave of absence.
In Bolton’s case, though, injury has been an untimely intervention.
Jackett said: ‘Bolton collected a groin injury in Ireland, which is slightly frustrating.
‘He will be out for a week, maybe two, although it’s not a major one.
‘I certainly don’t think he will play Tuesday at Bognor or Saturday either.
‘Hawkins is close to a return, we hope by the back end of next week both him and Ryan Williams will be there or thereabouts.
‘I don’t think it will be Saturday (Stevenage), I would think more likely the week after.
‘As for Ross, I decided on Friday to give him the weekend off to get back up to Scotland and hopefully sort a few things out.
‘He can then come back on Monday and potentially stay down.’