Naitanui, who has been battling an Achilles injury in recent weeks, has been ruled out of this Saturday's clash against North Melbourne.
The 32-year-old will be in the mix for selection in the following weeks as the club takes a cautious approach to his recovery.
“Nic has been working diligently with our strength and conditioning team to return to play as soon as possible and is making encouraging progress,” Eagles football boss Gavin Bell said in a club statement.
“When Nic does return we want him to play with the same unique explosiveness and power around the contest that we've all come to know and admire about his game.
“While he continues his positive progression, Nic won't be available to play North Melbourne in round one at Marvel Stadium this Saturday.”
While Naitnui's absence comes as a blow to the Eagles' Round 1 plans, the club has confirmed a trio of AFL debutants to face the Kangaroos.
2021 first-round pick Campbell Chesser will make his debut following a rookie season spent on the sidelines, with the Sandringham Dragons product impressing coaches since returning to full fitness over the pre-season.
Fellow 2022 draftee Noah Long is the third Eagle set to make his debut against North Melbourne, with the small forward having shown positive signs since joining the club as the 58th overall pick in last year's draft.
West Coast have also confirmed free agency recruit and former Demon Jayden Hunt will play his first match for the club this weekend.
Hunt made the move from Melbourne to West Coast at the end of last season following 114 games in the red and blue.
West Coast will travel to Melbourne this weekend to face the Kangaroos at Marvel Stadium at 1:45pm (AEDT) on Saturday.