Kenny Jackett' s side are aiming for successive League One victories following their win at Oxford United on Tuesday.
It was workmanlike but the Blues delivered a much-needed 1-0 success against Karl Robinson’s in-form hosts.
Harvey White bagged his maiden senior goal to cement Pompey’s berth in the play-off places.
And with 17 games remaining, the Blues still harbour ambitions of being promoted automatically.
Jackett now has to ponder whether to go with the same side that beat Oxford or make changes against Gillingham.
Gills chief Steve Evans will be expecting a response from his troops after slamming some of them following their loss to AFC Wimbledon in midweek.
Certainly, it’s a tricky game for Pompey and Jackett will have to get his selection spot on.
Here's how we think the Blues will line-up...
5. Left-back - Lee Brown
Came back into the side at Oxford and offered leadership to the defence that's been lacking. Pompey will need that presence again. Photo: Joe Pepler
6. Right-midfield - Ryan Williams
The Aussie came on and had a fine impact against Oxford. He's surely banging on the door to replace the out-of-form Marcus Harness. Photo: Graham Hunt
7. Centre-midfield - Tom Naylor
The first name on the team sheet, as per usual. Photo: PinPeP
8. Centre-midfield - Andy Cannon
The ex-Rochdale man had been looking leggy before bounce back emphatically against Oxford. Photo: PinPeP