Smith tweaked his positioning at the crease in Perth, shuffling across his stumps, and everything clicked. He scored his first test century on home soil and swung momentum Australia's way.
It was rewarded with official man-of-the-match honours but also the revered garment that coaching staff present to Australia's best performer behind closed doors after a test.
"I can remember when he accepted the man-of-the-match jacket, he was really emotional," Chris Rogers recalled. "He was almost a bit teary. Because he'd just felt under so much pressure, he'd felt quite insecure about his spot.
"That hundred defined him. It was one of the early steps on this path to being not only a different batsman but a different person, going from that kid who was a little bit of an Aussie grommet to now being this captain who makes tough decisions, leads from the front and carries the side at times. It just means so much to him."
Smith's average of 74 as captain only tells half the story of his leadership style, according to Rogers.
"He's just so determined to do well and it's infectious," the former test opener said.
Smith remains a fresh-faced fidgeter at the crease but his presence is now the personification of leadership. Teammates at the non-striker's end walk taller and play better with Smith. Mitch Marsh spoke of how the skipper's "aura" helped settle him during his maiden test ton.
England's coach Trevor Bayliss knows the world's best batsman well through their shared time at NSW and the Sydney Sixers. Despite Bayliss's inside knowledge and oodles of opposition analysis, England are yet to crack the Smith code.
They aren't alone.
Smith's blend of child-like exuberance and fierce competitive streak has resulted in mountains of runs around the cricketing world.
Fans also remain fascinated by the captain's quirks.
Smith's bat transforms into a lightsaber during a tense duel, his shoelaces are taped to his legs because they're distractions. He flashes indignant looks at inconsistent bounce, furrows his brow at failed reviews and is a picture of euphoria at the fall of a key wicket.
Josh Hazlewood is among the few who know the man behind the mannerisms. The pair have shared the journey from NSW junior ranks to international stardom.
"You see on the field how meticulous he is ... and off the field he can't sit still either. He's always up and about," Hazlewood said.
"He's a great leader. His relationship with the bowlers is very good. You need honesty and it's one of his best traits."
Smith's voice has grown steadily louder, publicly and privately, since he was appointed captain after Australia's failed 2015 Ashes campaign in England. The exception is a spike after the loss in Hobart last summer that led to an overhaul of his XI.
"He handled that situation very well. It probably left a mark, he's definitely a bit different since that moment," Hazlewood said.
"You're always probably going to be a bit more cautious when you start out ... he's definitely a bit more proactive now."
Smith has always been a man of conviction who doesn't bother with pretence or poker faces. But he now more readily and happily pushes back if poked.
Recently he highlighted the hypocrisy of "one of the biggest sledgers in the game" Jimmy Anderson and dismissed allegations he rules selectors as "absolute garbage".
His tactics have also been regularly critiqued this summer, most notably failing to enforce the follow-on in Adelaide.
"It's one of the biggest jobs in Australia. There's a lot of pressure," Johnson said. "He's doing everything the way he feels is best ... and he's getting better and better."
- AAP
