Among those numbers are influential first-team regulars Marcus Harness, Louis Thompson and Michael Jacobs as well as Player of the Season Sean Raggett.
Danny Cowley revealed the Blues are yet to finalise talks with any of his out-of-contract contingent over new deals – opening up the possibility of them leaving for free come June.
But how does the Fratton Park outfit’s numbers of potential free agents compare to those across the rest of League One?
We’ve taken a look at the sides with the most players out-of-contract in the summer and who could have the biggest rebuilding job ahead.
Here’s what we found.
17. Pompey - 10
Out-of-contract players: Ronan Curtis, Josh Oluwayemi, Michael Jacobs, Ryan Tunnicliffe, Connor Ogilvie, Clark Robertson, Kieron Freeman, Louis Thompson, Jay Mingi, Jayden Reid. Photo: Jason Brown
18. Charlton - 11
Out-of-contract players: Michael Hector, Macauley Bonne, George Dobson, Sean Clare, Ashley Maynard-Brewer, Albie Morgan, Ryan Inniss, Terrell Thomas, Nathan Harness, Charles Clayden, Aaron Henry. Photo: Naomi Baker
19. Port Vale - 11
Out-of-contract players: James Wilson, Nathan Smith, Ben Garrity, Jamie Proctor, David Worrall, Tom Pett, Dennis Politic, Mal Benning, Dan Jones, Sam Robinson, Aidan Stone. Photo: Morgan Harlow
20. Exeter - 12
Out-of-contract players: Jamal Blackman, Josh Key, Jevani Brown, Kevin MacDonald, Pierce Sweeney, Archie Collins, Alex Hartridge, Gary Woods, Jack Sparkes, Cheick Diabate, Scott Brown, Harry Kite. Photo: Pete Norton