Boak was not named in Port Adelaide's 22-man side to face Brisbane when teams were revealed on Thursday evening, with the 34-year-old continuing to battle an injury sustained in last month's pre-season matchup with West Coast.
A collision with Eagles defender Jeremy McGovern left Boak hampered and unable to return to the field for the match, with the onballer cleared of serious injury shortly after.
A recent diagnosis has revealed a fracture in Boak's ribs, an ailment that will keep the club's record games holder on the sidelines for the foreseeable future.
Hinkley revealed to media on Friday that the club is unsure on an accurate timeline for Boak's return.
"Initial scans in Perth were clear, but as it settled down a fracture has appeared," Hinkley said.
"He has a slight crack in the rib. We don't absolutely know (how long is required for recovery) but we hope it is short term.
"It is hard to determine when that will get better."
The Power are also without key forward Jeremy Finlayson for their season opener, with pre-season ankle surgery containing to keep the former Giant off the field.
Hinkley said while the club is keen to have Finlayson back in the selection mix, more time is needed for the forward's recovery.
"He needs the best preparation," Hinkley said.
"We are hopeful Jeremy will back in the side real quick."
Finlayson is set to feature in Port Adelaide's SANFL trials in the coming weeks as he eyes a return to the top flight.