The Australians will take on the wounded Pumas in San Juan on Sunday morning (AEST) looking to back up last week's 41-26 victory.
Leading up to that opening Test they lost skipper Michael Hooper (mental health) and hooker Dave Porecki (concussion) while veteran playmaker Quade Cooper ruptured his Achilles during the game.
Ahead of this clash Hunter Paisami has been ruled out after a head knock, with Wallabies coach Dave Rennie naming Waratahs centre Lalakai Foketi for his second Test appearance.
He will start at 12, with Len Ikitau returning at outside centre.
The inexperience of Foketi has led Rennie to opt for the cool head of 63-Test veteran O'Connor ahead of youngster Noah Lolesio, who wore the 10 jersey through the recent England series.
Prop Allan Alaalatoa became the fourth member from the Wallabies squad to fly home from Argentina following a family bereavement, with Taniela Tupou the starting tighthead.
"Giteau's Law" choice Rory Arnold, who has been based in France, will have his first start of the year in the second row, replacing Matt Philip.
Giant Melbourne enforcer Pone Fa'amausili has been named to make his Test debut from the bench.
Irae Simone, who was a late call-up to the squad and will head to France following the two-Test tour of Argentina, has been named on the bench for his third Test with Rennie adding an additional back.
Wallabies: Tom Wright, Jordan Petaia, Len Ikitau, Lalakai Foketi, Marika Koroibete, James O'Connor, Nic White, Rob Valetini, Fraser McReight, Jed Holloway, Darcy Swain, Rory Arnold, Taniela Tupou, Folau Fainga'a, James Slipper (c). Res: Lachlan Lonergan, Matt Gibbon, Pone Fa'amausili, Nick Frost, Pete Samu, Tate McDermott, Irae Simone, Reece Hodge.
