The 26-year-old former Norwich man is sidelined with a fractured rib and punctured lung sustained in their 1-1 draw with Northampton and looks set to miss the next two months.
Ling, who began his playing career with the Grecians, could give Billy Bodin the nod if he shakes off an ankle injury or play Nathan Craig behind targetman Rene Howe while Ashley Yeoman comes into contention.
Torquay remain without Ian Morris (Achilles) and Lloyd Macklin (broken metatarsal) while centre-back Brian Saah will miss out through suspension for his straight red card at Bradford.
The Gulls boss also announced this week that he will not be offering a contract to attacker Eric Odhiambo. The former Leicester and Inverness man spent a two-week trial with the Gulls.
Torquay welcome their Devon rivals having lost just once at home all season but only Gillingham have a better away record than the Grecians who have won 22 points on their travels.