Clark Robertson (Rotherham), Shaun Williams (Millwall) and Ryan Tunnicliffe (Luton) have all been snapped up on free transfers.
However, the Blues are one of several clubs in League One with designs on promotion in the 2021-22 season.
Here’s the latest transfer news from around the third tier.
Keeper snubs Man Utd for Wigan
Ben Amos has reportedly turned down a move to Premier League giants Manchester United - in favour of Wigan Athletic
The goalkeeper left Charlton at the end of last season, having let his contract run down.
Ipswich have been linked with Amos throughout the summer.
Yet Mail Online claim that the Red Devils were keen to bring Amos – who started his career at Old Trafford – back as cover for David De Gea and Dean Henderson.
However, Amos has instead chosen to join Wigan where he will play regular football.
The Latics have already signed ex-Pompey duo Jack Whatmough and Tom Naylor during the transfer window, along with the likes of Max Power and Gwion Edwards.
Ipswich seal Bonne move
Ipswich have swooped for QPR striker Macauley Bonne.
Bonee, who has previously been linked with Pompey, has signed a season-long loan at Portman Road.
The ex-Leyton Orient man scored just three goals in 35 appearances for the Londoners last campaign but has now joined the club he grew up a fan of.
Bonne told the club's website: ‘I’m a Town fan and as soon as I heard about the opportunity to come back here and play for the first-team, the team that I essentially love, it was a no-brainer. I can’t wait to get going now.
‘Paul Cook is a character. He’s been dying to get it over the line. He seems like a guy I really want to work with and do well under, and it seems like he wants the same for me so that’s all I can ask for.’
Wednesday slap £5m on Windass
Sheffield Wednesday have slapped a whopping £5m price tag on Josh Windass, according to The Sun.
Windass has attracted plenty of interest following Darren Moore's side's relegation to League One.
The likes of Millwall, Birmingham and Preston have all been linked with the 27-year-old.
However, the hefty fee they'll supposedly have to pay will likely put off any potential suitors.
Windass scored 10 goals in 44 games for Wednesday last season.