Kal Naismith will miss Pompey’s clash against Northampton in the Checkatrade Trophy on Saturday (12.30pm).
The Scot netted the winner in the Blues’ 1-0 defeat of Plymouth last time out.
But he limped out late in the game with a knee complaint after colliding with Pilgrims goalkeeper Remi Matthews.
As a result, Naismith will be absent for the Cobblers’ visit to Fratton Park.
Meanwhile, Brett Pitman and Dion Donohue remain sidelined after missing the win against Derek Adams’ side – with hamstring and lower back setbacks respectively.
Oli Hawkins also will not feature against Northampton after coming off injured with a hamstring complaint against Plymouth.
Boss Kenny Jackett is hopeful to have the quartet back for Pompey’s trip to Charlton on December 9.