To his right, Alessandro Circati is 22 but plays like a seasoned veteran, while 24-year-old wing-back Jacob Italiano is only getting better.
Souttar is still just 27 himself but is the elder statesman of a starting backline Tony Popovic - a former imposing centre-back himself - trusts to get the job done.
"It's really exciting," Souttar told AAP.
"Obviously, I'm not one of the older ones yet, but I'm probably in that middle to older group this time, whereas I was in as one of the young ones last time (in Qatar).
"It's really exciting to see the talent."
It's easy to see this starting backline, which played together for the first time against Mexico, rolled out again in Saturday's (5am Sunday AEST) friendly against Switzerland - and potentially the June 13 World Cup opener against Turkey.
Popovic has made one thing clear: young players getting an opportunity now have earned their shot.
Nobody is getting gifted a game - but by the same token, young players aren't just there to sit on the bench and watch on.
This is a defence for now, not just the future - as exciting as it is.
"Obviously that's the backline the boss decides, and I'm sure he decides it not on age but decides it on what he thinks is the best backline to go out and try and win the game," Circati told AAP.
"And then the age is a plus side, because every year that goes past, you gain a bit of experience, bit of knowledge, and I think it's quite exciting for the future as well.
"If that's the backline that it is now, and then for the future, then it just shows how strong that we can actually become."
Make no mistake - Popovic has still loaded up on plenty of defensive experience.
Versatile Kai Trewin is 25 but the other defenders sitting in reserve - Cameron Burgess, Aziz Behich, Milos Degenek and Jason Geria - have an average age of 32.5.
All of them keep the competition for spots high and are ready to step in.
"Obviously, we've still got other defenders there, like Cam, Jase, Milos always pushing us," Souttar, who played his first Socceroos game since November 2024 against Mexico, said of the centre-backs.
"The three spots are certainly up for grabs. No spot's guaranteed.
"You've got kind of six centre-halves that are all really good quality, all fighting for those three positions."
Australia face Group D opponents Turkey in Vancouver on June 13 (June 14 AEST), the United States in Seattle six days later then Paraguay in Santa Clara on June 25.
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