Having delivered a try and the hit of a lifetime to deny Springboks winger Makazole Mapimpi in Adelaide last week, Koroibete will face off against a teenager whose maturity has been widely praised.
Moodie has only played one season in South Africa's top club competition but looks an X-factor winger who will test the Wallabies as the Springboks try to avenge their loss and keep their Rugby Championship hopes alive.
"He's really good and I'm not even nervous for him - he's here for a reason," Springboks captain Siya Kolisi told reporters.
"He wants to learn, he's very quiet and doesn't talk a lot, but once he gets told to do something or he gets shown something he takes it in straight away and he's always keen to do extras and help the other guys as well.
"I remember playing against him … some of the stuff he was doing, you wouldn't think he was in school just a couple of years ago."
Assistant coach Mzwandile Stick agreed Moodie was ready for the Test arena despite his young age.
"We've seen what he has done for the Bulls - a very, very tough kid as a 19-year-old to be able to put physical hits on like that," he told reporters.
"When it comes to the positions where they're playing he is going against Koroibete, but if we play well as a team, even if the guys around him keep on motivating him, I'm not worried at all what's going to happen.
"Yes, it's a big challenge, but on the other side, I'm excited to see."
It's a crunch encounter for the Springboks, their Championship hopes will be snuffed if they fall to the Wallabies at Sydney's new Allianz Stadium
Addressing a growing frustration from Soutn Africa supporters, Kolisi said taking similar chances to the ones they created in Adelaide would put them in the box seat.
"People can say whatever they want, we created over 28 opportunities to score tries," he said.
"The only thing is that we didn't take them as a team, but the way we play we are getting opportunities to show what we're made of."
