Nick Phipps and Samu Kerevi have been ruled out of Australia's three June Tests due to ankle injuries.
Kerevi suffered his injury during Queensland Reds' Super Rugby loss to Blues on Friday, while Waratahs' Phipps was hurt on May 27.
The duo have been replaced by Waratahs pair Jake Gordon, who is uncapped, and Rob Horne for matches against Fiji, Scotland and Italy.
"It's really unfortunate for Samu and Nick but a great opportunity for Jake and Rob to come into the squad," Wallabies coach Michael Cheika said.
"Jake was involved in our camp in Canberra earlier this year and has really stepped up for the Waratahs in Super Rugby. He's another uncapped player but it will be good to expose him to the Test environment.
"Rob has been a strong leader in our Wallabies environment and his experience will be invaluable in this relatively inexperienced squad.
"We really want to put a strong emphasis on leadership in this team and we have some young leaders in this squad who are continuing to develop."
The Wallabies face Fiji on Saturday before taking on Scotland (June 17) and Italy (June 24).
-- Qantas Wallabies (@qantaswallabies) June 4, 2017