And the former Arsenal prodigy says there's no reason why the Socceroos should be scared of doing so at this year's World Cup.
Socceroos boss Tony Popovic could on Thursday name 18-year-old defender Lucas Herrington in his squad for this month's friendlies against Cameroon and Curacao.
Herrington, who has thrived since moving from Brisbane Roar to MLS club Colorado Rapids, wasn't in the latest Young Socceroos squad, but Popovic said last week he was "not opposed to looking at him for now or the World Cup".
The Socceroos boss previously backed centre-back Hayden Matthews to start aged 20 in a World Cup qualifier in November 2024, and Nestory Irankunda became a regular starter at 19, and Mohamed Toure, 21, has led the line.
The late Sven-Goran Eriksson selected a then 17-year-old Walcott in his England squad for Germany 2006.
While Walcott didn't take the field, he believes there's merit in testing youngsters - like himself and ex-teammate Aaron Lennon back then.
"They just surprise you," Walcott told AAP.
"Because over time, you're going to have to adapt your game differently and then people find out your game, and you've got to try and do something different.
"It's the unknown factor I focus on, it terrifies opposition.
"You need that bit of luck, but you need that licence and to not be afraid to make mistakes, because essentially you grow and you learn from those."
Walcott also stressed patience with talented youngsters.
"It was a big build-up with me. I didn't play for a period of time, and then there was expectation to literally hit the ground running straight away," Walcott said at Stan Sports' Premier League trophy tour.
"But I had to do it at my own pace, and that's where my strength was. I didn't focus on anyone else, I'd focus on 'as long as I do it at my own pace I'm not going to let anyone try and derail me'."
Goalkeeper Joe Gauci could also return to the fray after being overlooked recently.
Gauci, 25, is in form while on loan at Port Vale from Aston Villa, including reaching next month's FA Cup quarter-final against Chelsea.
"He'll definitely be in the mix come the choices, in my opinion, not only for these games but for the World Cup," former Socceroos and Villa shot-stopper Mark Bosnich told AAP.
"I had a very, very lucky run in terms of my career, but it's not always smooth, and it's fantastic that he's gone out on loan.
"He played a prominent part in Port Vale's massive upset against Sunderland in the FA Cup. That wonderful FA Cup win will do him absolutely no harm - it'll actually be brilliant for him.
"Absolutely phenomenal that he's playing out on loan. And I believe within time that he will be in the Premier League, whether it'll be back at Villa or somewhere else."
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