In the four-and-a-half years since his memorable Ashes debut at Trent Bridge, Ashton Agar has shed the boyish brown hair and gained plenty of experience about spin bowling, international cricket, and life.

His recall to the Australian Test team as a second spin bowler in the squad for the SCG match - a tradition in itself - is far from the surprise that surrounded his selection ahead of Nathan Lyon in 2013, having toured India as an intern earlier in the year. That experience was an adrenaline rush for many, particularly when he put together a masterful 98 at No. 11 alongside Phillip Hughes.

But it is now generally accepted that Agar needed more time to develop his skills as a bowler and a lower-order batsman, something that he has now gained over numerous years of struggle and improvement. "I don't look back on that too much," Agar said. They are great memories, but I've definitely moved forward since then and I feel like I've improved as a player.

"I was a kid. I was 19... I'm certainly better for the experience. I've grown up a lot since then. Life experience and cricket experience. I'm still reasonably young, but the time is now, so I'm just going to give it a good crack."

Agar's first state captain, Michael Hussey, has written about the whirlwind of Agar's initial selection. "After just three first-class games, the Australian selectors invited him on a national team tour to India to be a net bowler and gain experience from being around the team," Hussey wrote in Winning Edge. "It sounded like the right thing to do, but the alarm bells went off for me immediately. I knew he would bowl really well, I knew the selectors had doubts over Nathan Lyon, despite investing eighteen months of hard work in him, and I had a sneaking suspicion they would see Ashton as the bolter who could fix everything.

"Unsurprisingly, Ashton turned heads while with the team in India. I remember getting a message from the assistant coach Steve Rixon saying, 'How good is this Ashton Agar? I think he should play the first Test in India.' I thought to myself, 'No way! Please don't make this mistake!' Ashton was nowhere near ready. In my opinion he needed three or four seasons of first-class cricket to learn and grow and have some idea of what he would be in for if he was to play Test cricket.

"The selectors did not pick Ashton to play in India but he was thrown into the side for the first Ashes Test not long afterwards. I felt it was a huge mistake. Like in India, playing in the Ashes is akin to being in a cauldron. There are a multitude of distractions. There is so much hype and expectation. There are functions to go to, people to meet and huge interest from the media. There was no way this young fella could have been ready for that. For him to come out and score runs in his first match was a great achievement but it also created a perfect storm."

Hussey then watched as Agar slipped from public view and wrestled with his youth and his game. "For some time after the Ashes, Ashton was on a high while the public raved and the media loved him. But the wickets began to dry up," Hussey wrote. "The harder he tried, the worse he performed. He became frustrated and had too little experience to draw from to help him to change course. Eventually, he got suspended in a match for showing dissent to an umpire.

Ashton Agar celebrates his first wicket in Test cricket Getty Images

"Ashton went from Ashes superstar to possible has-been in an alarmingly short time. In my opinion the whole episode was very poorly handled. The duty of care to this young Australian cricketer was pretty much ignored. If everyone associated with making the decision to pick Ashton had just been patient and let him develop, he would have held on to his youthful zeal, grown gradually in confidence, expanded his knowledge and been much better off in the long run.

"He could have made the regular mistakes that young guys do and worked his way through them away from the spotlight. He should have been given space to learn about bowling, learn about life and enjoy the maturing process. I believe Ashton will come through this chastening experience and become a fantastic player. But I worry it will happen a lot later than it otherwise would have."

At 24, Agar is now in the position where the selectors wish to employ him as often as conditions will allow, the better to help him grow into the sort of spin bowler Australia will need for future Asian assignments such as facing Pakistan in the UAE in 2019, before facing India once more in 2021. At the same time, he has worked to better groove his bowling action, evidence of which was seen in Bangladesh earlier this year. Other spin bowlers, such as Jon Holland, Steve O'Keefe and Mitchell Swepson, have also emerged, but there is no question about the preference for Agar in the minds of the selectors.

"We've worked on my action a little bit a few years ago. Its just been a lot of bowling and self-confidence," Agar said. "All you've got is yourself out there and it's certainly grown. It's more just understanding my basics and how to consistently bowl my best ball - which is what you have to do in Test cricket.

"You have to consistently hit that length and challenge the batter's forward defence, so that's what I've worked on. I feel better coming into a Test match now. It doesn't feel too fresh or too out of the blue. Playing the one-dayers in India was a pretty whirlwind experience. So I certainly feel a lot better walking out onto the SCG now."

Lyon, of course, has made enormous strides in that time too. Four years after Agar unseated the older Lyon, the pair may now finally play an Ashes match in tandem.