Naitanui has been battling an Achilles issue in recent weeks, and it appears increasingly unlikely he will be fit to take on North Melbourne at Marvel Stadium on March 18.
"It's March, so we need to take our time with it," Simpson said at the club's season launch on Thursday.
"Is he right for round one? I can't answer that just yet, (but) he is doubtful."
Simpson is hopeful Darling will win his race to be fit for the round-one clash.
Darling injured his ankle last month, but avoided surgery and is pushing hard to be fit for West Coast's season opener.
"He trained today. We're hoping he is on target for round one. He is ticking boxes," Simpson said.
Simpson confirmed Shuey, who missed last week's practice match against Port Adelaide after being "managed", would return against the Crows.
Jack Petruccelle and prized first-round draft pick Reuben Ginbey will also play.
"He will start. It was a minor toe injury last week," Simpson said of Ginbey, who has impressed West Coast's coaching staff since being selected with pick No.9 at last year's national draft.
West Coast won just two games in an injury-ravaged campaign last year, but the Eagles are fitter and healthier this pre-season.
"We just want to improve. We want to be competitive," Simpson said.Â
"We want to win for our crowd at home. We need to improve, be competitive and hopefully the wins come after that."
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