Swallow, who managed only six games in 2015 due to a PCL injury, underwent arthroscopic surgery in Melbourne on Tuesday after experiencing soreness in his knee.
“David had an arthroscopy after experiencing some discomfort in his left knee,” general manager of football operations Marcus Ashcroft said.
“The arthroscope revealed that David’s recovery hadn’t progressed as well as had hoped and as a result his return to football will be delayed.
“Our medical team will review the information and consult further. We will have a clearer picture regarding ongoing management later in the week.”