Stuart O’Keefe has been ruled out for up to three months with an ongoing hernia injury.
The Cardiff loanee picked up the problem in Pompey's win over Bury in December and has been sidelined ever since.
As a result, O’Keefe recently underwent an operation for a hernia-type setback and Kenny Jackett has confirmed he will be out for 10-to-12 weeks.
The Blues boss had previously revealed the former Crystal Palace midfielder would be absent for four-to-six weeks.
Meanwhile, Gareth Evans will miss Saturday's trip to Rotherham due to a hamstring complaint that has forced him to miss Pompey's past three matches.
The Blues had previously been optimistic the winger would be fit for the clash at the New York Stadium, although Evans should return for Shrewsbury's visit to Fratton Park on January 27.
Jack Whatmough (knee) and Milan Lalkovic (Achilles) are both working their way back to full fitness, while Danny Rose (broken leg) is out for the remainder of the campaign.