Naitanui hasn't featured at all this year after being grounded by an Achilles issue during the pre-season.
What started as a short-term injury ballooned into a long-term problem.
Up until last week West Coast were hopeful Naitanui would be able to return at the tail-end of the campaign.
But a recent scan confirmed Naitanui now requires surgery in order to fully recover from the tendon injury.
That surgery is expected to take place next week and Simpson is holding out hope of Naitanui playing again in 2024 - the final year of the 33-year-old's contract.
"Hopefully we can get this right and he can work through the rehab and we see him next year," Simpson told reporters on Wednesday.
"I know it's something you can fully recover from.
"It's just a long stint out, so therefore the season is out of the question.
"I don't think it has (ruptured). But it's got to the point where it needs surgical intervention to fix it.
"It's been unfortunate this year. It came out of the blue a little bit in the pre-season. It's something you can get over for sure."
Naitanui's latest blow continues a torrid run on the injury front for last-placed West Coast, who now have a staggering 21 players on their injury list, with only four of those a chance to return this week.
The Eagles will be forced to make at least six changes to their side for Saturday's clash with the Crows in Adelaide after Shannon Hurn (hamstring), Elijah Hewett (concussion), Josh Rotham (finger), Callum Jamieson (hip), Connor West (knee) and Liam Duggan (infection/suspended) were all ruled out.
Tom Barrass, who was a late withdrawal from last week's loss to Collingwood with a hip injury, won't be available to return until after the bye.
Jamie Cripps, Jeremy McGovern, Liam Ryan, Tom Cole and Jamaine Jones are other notable names who are still out.
Captain Luke Shuey (ankle/hamstring) is set to return against the Crows and he could be joined by Jack Darling (fractured arm), Luke Edwards (concussion) and Samo Petrevski-Seton (corked leg).
Even if all four are able to return West Coast may need to hand a debut to raw ruckman Harry Barnett in order to inject some much-needed height into the side.
The injury toll to the senior side means West Coast's WAFL outfit may have as little as one Eagle in their ranks this weekend.
Duggan spent two nights in hospital after a cut in his toe became infected, but he is now out of hospital and will be ready to return after next week's bye.
"We were a bit worried there for a tiny bit, but it was fixed pretty quickly and he'll be fine post bye," Simpson said.
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