The midfielder has already had an x-ray on his ankle but he now faces further checks to get a better idea on the exact length of time he will be sidelined for.
Jones had only just returned to training after missing part of pre-season with a tight hamstring when he fell awkwardly on his ankle in the session before the squad boarded the bus for Gillingham.
And while it is not known for sure yet when the all-action competitor will be ready for a return, Parkinson is ready to accept that he will be without Jones' services for the immediate future.
"We've had an x-ray done on Ritchie's ankle and we're now looking to have it scanned once the swelling has gone down," Parkinson said.
"This should give us a better idea of exactly how long he will be sidelined for.
"We are pretty sure it will be a minimum of four weeks though."