Cadman will be sidelined for at least two weeks with ongoing pelvic soreness after sitting out the club's practice match against Sydney.
The former No.1 pick will miss Saturday's opening round elimination final rematch at Engie Stadium against Hawthorn, before the round-one away game against the Western Bulldogs.
Now part of injury list featuring 11 Giants, Cadman joins teammates including midfield bull Tom Green (knee) and Josh Kelly (hip).
The club are at least hopeful star on-baller Finn Callaghan (hip flexor) will be available this Saturday, while Toby Bedford (hamstring), Leek Aleer (groin) and Toby McMullin (hamstring) are one week away.
But small forward Brent Daniels (hamstring) could spend up to four weeks on the sidelines, while Sam Taylor (hamstring) could be sidelined for as long as six weeks.
Green is out for the season, with the club hopeful Kelly and young gun Darcy Jones (knee) will return in the second half of the campaign.
Elsewhere, Collingwood confirmed on Tuesday captain Darcy Moore and fellow defender Jeremy Howe won't be available to play against St Kilda on Sunday night.
Magpies coach Craig McRae had last week said the pair were unlikely to line up due to separate calf injuries sustained over the summer.
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