After surprisingly omitting Cooper for the Wallabies' 33-man World Cup squad last week, now coach Eddie Jones picked fellow veteran Bernard Foley as five-eight for the back-up group.
Portugal are one of the Wallabies' four rivals in Group C of the World Cup and their hit-out against Australia A on August 26 will be Os Lobos' final match before their first tournament opener against Wales on September 16.
The match also shapes as a vital clash for a host of players in Jason Gilmore's Australia A side hoping for a call-up during the showpiece in September and October.
But Cooper's prospects of a farewell World Cup are effectively over.
After being Robbie Deans' go-to playmaker in New Zealand in 2011, Cooper barely featured under Michael Cheika in the 2015 edition in the UK.
He then missed selection in Cheika's 2019 squad in Japan.
The 35-year-old was Jones' first-choice No.10 for Australia's first two Tests this season before being relegated to the bench behind Carter Gordon and now completely dumped altogether.
But there has been a reprieve for Cooper's long-time former teammate James O'Connor, who has been picked as one of the centres named on Tuesday and to be coached by NSW Waratahs assistant Gilmore.
"It is a quality squad with a good mix of experience and youth throughout," Gilmore said.
"This is a valuable opportunity for these players, playing on the doorstep of the Rugby World Cup, just days before it kicks off.
"However the most important thing for us will be to play well together as a team.
"The Rugby World Cup is a long tournament and history suggests you rarely finish with the same squad that you begin with.
"The players are aware of the possibility that the Wallabies may need an injury replacement and this is an opportunity for them to put themselves in the picture."
Australia A squad:
Props: Matt Gibbon, Harry Johnson-Holmes, Tom Lambert, Sam Talakai.
Hookers: Folau Fainga'a, Lachlan Lonergan. Locks: Josh Canham, Lukhan Salakaia-Loto, Darcy Swain.
Back-rowers: Ned Hanigan, Pete Samu, Lachlan Swinton, Seru Uru, Brad Wilkin.
Halfbacks: Ryan Lonergan, James Tuttle.
Five-eighth: Bernard Foley.
Centres: Filipo Daugunu, Josh Flook, James O'Connor, Hunter Paisami.
Outside backs: Lachlan Anderson, Dylan Pietsch, Corey Toole, Tom Wright.
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