The Blues will be aiming to pull off an upset against the Premier League hosts at the Amex Stadium.
Kenny Jackett has to weigh up the starting line-up against the Seagulls, with a League One trip to Rochdale on Sunday to also plan for.
The boss has said he wants some continuity, though, as he looks for Pompey to get into a winning rhythm.
Here's how we think the Blues could start...
5. Left-back - Lee Brown
It wouldn't be a complete surprise to see Cameron Pring start, but Jackett might not want to make too many changes to his defence while Brown's experience against a Premier League side will also be a bonus Photo: Joe Pepler
6. Holding midfield - Tom Naylor
Set to lead Pompey out at the Amex Stadium. Photo: Joe Pepler
7. Holding midfield - Ben Close
Pompey may not risk Bryn Morris, who has a hip injury and give Close a first start of the season. Will be keen to catch the eye if he does start. Photo: Joe Pepler
8. Right wing - Ryan Williams
Marcus Harness didn't have his best of games against Shrewsbury and Jackett may opt to give him a bit of respite. Williams will be fresh and determined if he starts. Photo: Joe Pepler