Cisak was dislodged as Latics number-one by Dean Bouzanis in mid-September and made his Pompey debut against Coventry last weekend.
But Bouzanis received a red card in the closing moments of Tuesday night's loss at Doncaster and must serve a three-match ban after shoving Rovers striker Iain Hume.
Providing Oldham are granted permission by the Football League to bring Cisak back, the 23-year-old is set to start when Paul Dickov's men meet the same opponents in the FA Cup on Saturday.
"We will be getting Alex back for Saturday," manager Paul Dickov told the Oldham Chronicle.
On the sending off, Dickov added: "It is silly for Dean. There is no need to go and get involved there."