Christian Burgess missed out on his 100th Pompey outing through injury.
The defender was sidelined with a calf problem collected in the mid-week victory over Bristol Rovers, so Nathan Thompson switched to centre-half.
That marked a recall at right-back for Drew Talbot in the only change to the side which won 3-0 on Tuesday night.
With Damien McCrory out with a twisted knee, Dion Donohue continued at left-back, while Conor Chaplin was again missing with a hamstring injury.
Talbot's promotion from the bench meant a return to the match-day squad for Danny Rose, taking his place among the substitutes.
Meanwhile, Oldham included former Pompey loanee Eoin Doyle in their starting line-up.
During the build-up, the striker had been ruled out of a Fratton Park return through injury, but was named in the team this afternoon.
Pompey: McGee, Talbot, Thompson, Clarke, Donohue, Close, O'Keefe, Lowe, Pitman, Kennedy, Hawkins.
Subs Not Used; Bass, Rose, Main, Naismith, Bennett, Evans, Haunstrup.