Centre-half Knight-Percival hobbled off midway through the second half of last Saturday's surprise 2-1 win at npower Championship leaders Cardiff.
Ferguson said: "Nat is fine. Obviously I never declare my team too early as I have to take into account the tactics and strength of the opposition, but it would be hard to make any changes after the performance at Cardiff."
Should Posh be unchanged, defenders Craig Alcock, Shaun Brisley and Kane Ferdinand, midfielders Danny Swanson and Grant McCann and striker Jaanai Gordon-Hutton, who scored twice in a FA Youth Cup win this week, could again make up the substitutes.
- Sports & Recreation