John Iafolla (Sieders Racing Team) shot off track between Turns 6 and 7, his vehicle getting airborne and ploughing through a barrier before barrel-rolling several times.
The car, upside-down, landed heavily on the tray of a recovery ute, stunning the officials inside, and eventually came to rest on its side, smoking heavily.
Iafolla could be seen moving inside the car and after a few minutes he was able to walk away to a nearby ambulance, helped by medical staff.
The race was immediately red-flagged and the rest of the field made their way back to the pits.
Iafolla was later taken by ambulance to a local hospital for further observations. He was said to be in a stable condition and was able to walk out the Sandown medical centre.
Aaron Borg tops the standings after winning both races on Saturday.
Extensive repairs are being made to the barriers at the crash scene with track action expected to be severely delayed.