Mundy, 27, left the open Dockers training session at Fremantle Oval on Wednesday morning after rolling heavily on his ankle.
The talented midfielder did not return to the training track to complete the pre-season session.
The latest injury blow could have an impact on Mundy's summer program but is likely not related to the ankle injury which plagued his 2011 season.
Mundy was limited to just 12 games that year, after being diagnosed with syndesmosis.
The injury also upset Mundy's pre-season preparations approaching last season, although the Dockers 2010 best-and-fairest winner still managed to make 22 appearances.
It is not known how serious the latest ankle trouble is for Mundy or whether he will be available for NAB Cup action starting next month.
The Dockers have been dogged by injury concerns over the summer, with talented youngster Anthony Morabito ripping the graft in his reconstructed knee early into the new year.
Morabito opted for controversial LARS surgery over another traditional reconstruction and started his rehabilitation late last week.
Fremantle captain Matthew Pavlich has worked through a limited pre-season because of a back problem, while giant ruckman Aaron Sandilands missed two key sessions to have a personal surgery.