Maister damaged the lateral hamstring tendon behind his left knee when he fell in pursuit of West Coast defender Eric Mackenzie in the dying stages of last Sunday's loss at Etihad Stadium.
The 27-year-old has kicked 10 goals in seven games this season, playing as the Saints' second tall forward alongside Nick Riewoldt.
He was sidelined earlier this season with a wrist injury, missing three games, including the Saints' clash against the Sydney Swans in Christchurch.
Maister, who was known as Beau Wilkes until the start of this season, joins Lenny Hayes (calf), Adam Schneider (hamstring), and Sam Gilbert (knee) on the Saints' injury list.
