West Coast will be without their three best forwards for the most crucial part of their home-and-away season after Mark LeCras became the latest to succumb to injury.
LeCras will be sidelined for a yet-to-be-determined period after undergoing arthroscopic surgery on his injured right wrist on Wednesday.
The 31-year-old, who underwent surgery on the same wrist earlier in his career, suffered the injury during last week's AFL loss to Essendon.
West Coast forward Jack Darling (ankle) is still at least three weeks away from resuming, while fellow spearhead Josh Kennedy (leg) will miss between two to three more weeks.
Kennedy (29 goals), Darling (28) and LeCras (22) are West Coast's leading goalkickers this year.
The Eagles (10-3) have slipped to third spot following consecutive losses.
Their top-four hopes will go on the line during the next few weeks when they take on the Crows (away), GWS (home) and Collingwood (away).
Simpson was unsure how long LeCras would be sidelined.
"We're just waiting on results - specialists and scans and all those sort of things," Simpson said.
"(His wrist) is a bit loose. We'll let that settle down and see what comes from it. It's a bit early to tell what the damage is.
"It's disappointing. We're losing forwards left, right and centre, and he was one with plenty of experience for us. So we've just got to find another way.
"Every club goes through certain stages throughout the year when they're hit with some challenges, and this is our turn."
Simpson swung All-Australian defender Jeremy McGovern into attack during the final quarter against Essendon last week.
But with defender Tom Barrass (back) still injured, Simpson might be reluctant to leave McGovern in attack for the whole game in Saturday's clash with the Crows at Adelaide Oval.
Former Port midfielder Brendon Ah Chee has been recalled to replace LeCras in attack, while young midfielder Brayden Ainsworth replaces axed defender Jackson Nelson.
Adelaide have made six changes, recalling Luke Brown, Rory Laird, Rory Sloane, Darcy Fogarty, Cameron Ellis-Yolmen, and Curtly Hampton.
But forward Tom Lynch couldn't be considered for a recall after suffering a mild concussion at training on Wednesday.
The Crows lost Eddie Betts (hamstring), Andy Otten (Achilles) and Sam Gibson (hamstring) to injury, while Patrick Wilson, Rory Atkins and Myles Poholke have been dropped.