During the televised announcement of his 32-man squad, coach Michael Cheika was forced to select only five back-rowers for the series starting next weekend.
This after a written plea to have the previously unheralded Crusaders loose forward made available was shot down.
Samu, born and raised in Australia, was widely tipped to be named in Cheika's squad after announcing that he would quit Christchurch for the Brumbies next season.
Cheika told rugby.com.au he "couldn't pick him [Samu]" — but expressed confidence in having the matter resolved as early as today.
"I've been told I can't select him but there is a spot for him there," Cheika said.
"At this point, the decision's in other hands. I'm not really involved in that part of it but I'm hoping that there'll be some more clarity about that tomorrow.
"We were keen to pick him in the squad but for a certain reason he wasn't able to tonight. We'll have to leave it at that for the moment but we'll see where it ends up."
Samu has been a prominent and at times impressive contributor for the Crusaders this year, carrying the ball well and showing plenty of energy and fury about his work.
However, at 1.85m and 101kg Samu's not really the sort of athlete that screams out as an obvious candidate to be playing test rugby — even if only Michael Hooper and David Pocock would be considered world-class loose forwards in Cheika's squad.
Samu signed with Tasman in 2014 and won a contract with the Crusaders in 2016.
In accepting that deal, he signed the so-called Schedule Three which means he made a commitment to play only for New Zealand national teams. Samu effectively needs NZR to sanction his temporary release from Crusaders' obligations.
NZR received a similar request from England earlier this year — at first refusing to budge before allowing the Hurricanes captain to represent Eddie Jones' squad against the Springboks in June.
The national body said they made an exception for Shields due to his long service and loyalty.
Samu doesn't have the same goodwill in the bank and then there is the added complication that it is the Wallabies – the All Blacks oldest and most fierce rival – who want access to him.
There is also the question of his contract with Tasman. He is due to play for them this year after Super Rugby, but that would become impossible if he is called up to play for the Wallabies during the Rugby Championship.
"We have received a request from Rugby Australia and we're in discussions, but nothing has been decided yet," said NZR head of professional rugby Chris Lendrum.
The expectation is that RA will feel confident that they will ultimately win approval for Samu to become a Wallaby in June. They will fancy they can negotiate a sensible outcome that releases Samu and compensated Tasman.
Despite NZR's insistence they control the release of their contracted players, no other nation supports them in that stance as World Rugby's laws are clear that all players picked for test duty in the designated.
Wallabies squad:
Props: Sekope Kepu, Tom Robertson, Scott Sio, Taniela Tupou, Allan Alaalatoa
Hookers: Brandon Paenga-Amosa, Folau Faingaa, Jordan Uelese
Locks: Rory Arnold, Adam Coleman, Izack Rodda, Rob Simmons
Loose forwards: Michael Hooper, David Pocock, Caleb Timu, Lukhan Tui, Ned Hanigan
Backs: Bernard Foley, Will Genia, Tom Banks, Kurtley Beale, Israel Folau, Dane Haylett-Petty, Reece Hodge, Samu Kerevi, Marika Koroibete, Tevita Kuridrani, Jack Maddocks Sefa Naivalu, Nick Phipps, Joe Powell, Curtis Rona