Naitanui, who has been sidelined all year with an Achilles tendon injury, announced his immediate retirement on Monday.
He joins fellow club legends Luke Shuey and Shannon Hurn in hanging up the boots.
West Coast won just two games last season, and they are last on the ladder this year with a 2-19 record and a woeful percentage of 50.6.
Barring an unlikely win against the Bulldogs or Adelaide in the final two rounds, West Coast will collect just the second wooden spoon in the club's proud 37-year history.
The last time it happened was in 2010, with the Eagles remarkably making the preliminary finals a year later.
The rebuild this time around appears set to be a longer and more painful one.
But Naitanui is optimistic things will change quickly, and he's backing Simpson and the rest of the coaching group to turn it around.
"I never forget, we won a wooden spoon in 2010, I was part of that, and we had some success in 2011," Naitanui said.
"I think it's going to turn really quickly, and I feel we've got the right group for it, the right coaches, the right administration for it."
Simpson's future has been a hot talking point this season.
Five losses in excess of 100 points, including an embarrassing 171-point defeat to Sydney in round 15, means Simpson remains on shaky ground.
Naitanui wished he was able to play this year to help take the heat off Simpson and the rest of the team.
One big positive about West Coast's woeful form is the fact they are on track to receive the prized No.1 pick in the national draft.
It means the Eagles can either snare gun Victorian midfielder Harley Reid, or trade the pick away to a rival club for up to three first-round picks in return.
West Coast finished 15th of 16 teams in 2008, and it allowed them to snare Naitanui with pick No.2 in that year's national draft, as well as Shuey with a priority selection pick (No.18).
"People forget sometimes that clubs go through these lulls. There's some down times," Naitanui said.
"A lot of us players wouldn't be in the room if it wasn't for some of those down times.
"Shuey and I came at the end of 2008. We were struggling and we were early picks.
"That's starting to happen now. You're seeing guys like Elijah (Hewett), Reuben (Ginbey), and Noah Long come through.Â
"They're that next generation of guys that are going to come and help the players above them get better and improve."
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