Crowley will fly to Melbourne on Thursday to have his injury assessed, but Harvey said his chief tagger would be out for three months with an ailment he compared to that of sidelined Hawthorn backman Trent Croad.
Harvey said Crowley and onballer Rhys Palmer, who sustained a season-ending knee injury in round five, would need to be replaced by hard-running players ahead of Saturday's clash with Carlton on the Gold Coast.
"It would be fair to say there's four or five names at the moment that we're looking at, some are on the rookie list," Harvey said from Fremantle Oval on Wednesday.
"We might need to actually put through some paper work quickly if you know what I mean.
"It's interesting, with losing the two guys that we have in the last week they're our sort of power runners, they're right up there with the elite runners – we have to actually select players that can hopefully fill the void in that area."
Harvey confirmed midfielder Andrew Foster would be considered after starring in his second game at WAFL level at the weekend.
The 23-year-old has been managed through a back injury and played a full game for the first time this season, finishing with 22 possessions and two goals.
"We hold him in really high regard," Harvey said. "He's only just starting to come back into some form that indicates that he's getting somewhere near selection.
"With the young group that we've got, we haven't got a lot of options. Hence he will be one we consider."
Rookie Clancee Pearce has also been in solid WAFL form for Swan Districts and looms as a possible elevation following the long-term injuries to Crowley and Palmer.
The other dilemma for Harvey is champion Carlton midfielder Chris Judd, who Crowley would likely have ran with this Saturday.
Harvey said he would look to give the job to a young player, but didn’t rule out captain Mathew Pavlich as a potential head-to-head match up at times.
"Our team needs to grow with younger guys having a look at a guy like Judd," the coach said.
"A guy like (Garrick) Ibbotson, that type of player. Even a young kid like Stephen Hill, but it might be a bit early for him."
Returning to WAFL football this week will be defender Greg Broughton, who has missed the last three weeks with an ankle injury after debuting in round three.
The news is not so good for Chris Mayne (ankle), who is recovering slower than expected. Harvey said he hoped the small forward would be available for AFL selection after the mid-season break.
Meanwhile, midfielder Andrew Browne will be unavailable for an indefinite period of time and Harvey said at this point it was important to respect Andrew's privacy.
