The cut-off point for clubs to complete their business is on Friday, October 16.
So far Pompey have made four signings. Sean Raggett was the first through the door, completing a permanent switch from Norwich after spending last season on loan at Fratton Park.
Cameron Pring following on a season-long loan from Bristol City, before Callum Johnson was recruited for around £200,000 from Accrington.
Then, last week, the Blues snapped up Michael Jacobs on a free transfer after he departed from Wigan.
While there won't be any wholesale changes at PO4 between now and the window shutting, we could still see couple of new faces arrive.
Pompey still want another centre-back, while a striker and central midfielder are other areas that could be bolstered.
The free-agent market could again be dipped into by Kenny Jackett and there are still plenty of unattached players available – although they can still be signed after the window closes.
We’ve taken a look at some of the unattached players who could fit the bill for Pompey…
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5. Will Keane
The striker is still without a club after departing Ipswich at the end of last season. Was highly rated as a youngster at Manchester United. Photo: Lewis Storey
6. Courtney Baker-Richardson
The striker was plucked from non-league by Swansea in 2017, having also had a trial at Leicester. The 24-year-old has also featured for Charlton during pre-season but is unable to sign because of their transfer embargo. Photo: Marc Atkins
7. Jacob Butterfield
The central midfielder has plenty of Championship experience, representing the likes of Middlesbrough, Sheffield Wednesday, Derby and Luton last season. Would bring nous. Photo: George Wood
8. Ashley Williams
Undoubtedly a longshot given his likely wage demands. However, with the Euros next year, Williams may feel he needs to be playing to be part of Wales' squad and drop to League One. Photo: Harry Trump