Midfielder Sam Foley has a badly sprained ankle but won't require surgery.
The summer signing left Saturday's Maunsell Cup Final on crutches with his foot in a protective boot but scans have revealed that while the ankle is sprained, no surgery is required.
Foley will miss Tuesday night's game when Derby County visit Sixfields (kick off 7.45pm) but recent signings Matt Crooks and Aaron Pierre could make their first appearances in a Northampton Town shirt.
Tickets for the game are available on arrival or via ntfcdirect.co.uk