The Republic of Ireland international has been sidelined for eight days with a glute problem collected during Pompey’s return to training.
He also missed Sunday’s friendly at Reading, in which the Blues suffered a 3-1 Madejski Stadium defeat.
However, Jackett expects Curtis to return to full training tomorrow as the Blues drive towards their League One play-off semi-final with Oxford United.
Another affected by injury is Reeco Hackett-Fairchild, who was also absent from yesterday’s friendly.
The left-winger is pencilled in to return from his quad muscle injury in a week’s time.
Pompey’s boss told The News: ‘I didn’t risk Ronan at Reading, had it been a league game he might have had a chance.
‘Reeco also missed yesterday and maybe out for a week, but there is plenty of time for both of them to get back for the Oxford game.
‘In Ronan’s case, there are no major problems with them. He felt his glute slightly, so we’re not going to risk him with three weeks to go.
‘He didn’t train with the group today, but was outside. He will be training with us tomorrow.
‘I have confidence now that for the next session he will be fine.’
Curtis has scored 13 goals and been one of Pompey’s key performers during the season.
He has roared back to form following a difficult start to the campaign, putting himself in the frame for player of the season accolades.
Meanwhile, Hackett-Fairchild has yet to make his league bow for the Blues since joining from non-league Bromley in January.
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