Centre Justin Hodges had already been ruled out this week with a shoulder injury and will require surgery. His likely replacement, St George Illawarra Dragon centre Matt Cooper, was then ruled out with a groin injury that will also require surgery.
Stewart was forced to withdraw this morning after receiving a cortisone injection for a shoulder injury.
The players will join the Kangaroos when the squad goes into camp in Sydney this Saturday. Australia's first World Cup match is against New Zealand on October 26 at the Sydney Football Stadium.