St Kilda have been forced into a late change ahead of Sunday's clash with Fremantle, with veteran Brad Hill ruled out of the match due to illness.

The Saints confirmed on Friday that Hill won't make the trip to Perth, with second-year defender Arie Schoenmaker named in his place among Ross Lyon's extended squad.

Hill's omission is the second confirmed change for the Saints, who will also be without backman Jimmy Webster, who has been managed.

Lyon could make as many as five changes for Round 16, with Jack Carroll, Hugo Garcia, Liam Henry, Harry Boyd and Schoenmaker among the potential inclusions.

Both sides will confirm their 23-player squads on Friday at 5:00pm (AEST), with final teams to be locked in an hour prior to Sunday's 5:10pm bounce.