Boak is sidelined by COVID-19 protocols while triple club best-and-fairest Gray has been sent for a spell because of a lingering knee injury.
The Power have also dumped experienced forward Steven Motlop and lost Trent Dumont to a calf injury for the Adelaide Oval fixture
Port coach Ken Hinkley has picked ruckman Brynn Teakle for his AFL debut just two weeks after being selected in the mid-season draft.
"In my time in football I have never seen anyone get their first game within 14 days," Hinkley told reporters on Thursday.
"It's one of the great stories of the mid-season draft."
The 22-year-old Teakle, plucked from Western Australia's state league, joins recalled trio Mitch Georgiades, Jackson Mead and Martin Fredericks.
And Hinkley said the quartet had some big holes to fill for a Power side slipping out of finals reckoning - they're 12th, three wins shy of eighth spot.
"There's about 900 games of experience leaving our side," he said.
Gray has battled with a knee injury all season after being hurt in round one.
"We had the bye and he still wasn't quite at his absolute best," Hinkley said.
"He just needs to get some continuity into his game and some training performance.
"He has tried to play for the 10 or 12 weeks without training and that is unsustainable no matter how good you are, and we know how great Rob has been.
"We won't put a timeframe on Robbie, just make sure he gets through the next couple of weeks of good training.
"Robbie had an absolutely outstanding pre-season and someone fell across his leg in round one in Brisbane and he just hasn't been able to get over it since then."All the things have been investigated and researched ,whether it did or didn't need some surgery or anything like that.
"It was purely around rest ... Rob has played with some discomfort and it's just getting to a point where non-training and discomfort together are just making it too hard for him to perform at his best."
12°C