The 31-year-old full-back suffered a groin injury during the second half of Tuesday night's 3-2 defeat against Yeovil and had to be replaced by David Noble.
Tully will be given as much time as possible to prove his availability but Tisdale may be forced to shuffle his pack if he fails to recover in time.
The Grecians boss could revert to a 4-4-2 formation with Noble taking up a midfield position and Scott Golbourne dropping back to left-back and Richard Duffy moving to right-back.
Tisdale has no other injury or suspension problems to worry about.
Strikers Marcus Stewart and Daniel Nardiello are both pushing for recalls following cameo appearances against the Glovers.
Source: PA
Source: PA