Former Test captain Greg Chappell has offered a fascinating insight into the mind of Steve Smith as the Australian moves into more exclusive territory among his country's fellow batting greats.

Smith passed Chappell's runs mark of 7,110 on day one at the MCG with a comfortable single in the 51st over, moving into 10th position on Australia's list of all-time Test run-scorers. Within that illustrious group, his average of 63.49 at the time he went ahead of Chappell is head and shoulders above the rest.

Australia's top 10 Test run-scorers

Ricky Ponting | 13,378 @ 51.85

Allan Border | 11,174 @ 50.56

SR Waugh | 10,927 @ 51.06

MJ Clarke | 8,643 @ 49.10

ML Hayden | 8,625 @ 50.73

ME Waugh | 8,029 @ 41.81

JL Langer | 7,696 @ 45.27

MA Taylor | 7,525 @ 43.49

DC Boon | 7,422 @ 43.65

Steve Smith | 7,111 @ 63.49 (when reaching 39* in Melbourne)

Smith had a year out of international cricket due to his involvement in Australia's ball-tampering scandal in March 2018, and has since said the time away both refreshed him and provided him with a better perspective regarding his life as a professional cricketer.

He returned to Tests in a blaze of glory in this year's drawn Ashes series, dominating to the tune of 774 runs at 110.57, and Chappell does not expect his remarkable run of form to end any time soon.

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"I would think he'll be in his peak for another three of four years," the 87-Test great told cricket.com.au. "He's the outstanding player of his era, he's playing exceedingly well and he's built up a record which is comparable with the very best.

"The indications are he's going to finish his career in the very top bracket of batsmen through the history of the game."

While his bouts of insomnia before and during matches have become a part of the Smith legend, Chappell believes the 30-year-old's obsessive – but optimistic – thinking about the game in fact serves him well.

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"He doesn't lie in bed worrying about getting out; he might be wide awake but he's excited about batting, and thinking about how he's going to make runs," he said.

"Most players spend a lot of their time anxious about whether they're going to make runs, and they hit a lot of balls to make up for that anxiety.

"Smith isn't doing that. He genuinely loves batting, and a lot of that hitting balls (in the nets) is just filling up the day, waiting for the real cricket to start.

"But the real work is done in his room, inside his head, preparing himself for the bowlers he's going to face. That's where he's honing his knowledge; he's seeing the bowlers bowl to him, working out the angles, so by the time he gets to the game, all he has to do is react.

"He's unique in that way – he has a mind that works differently. It's been brilliantly trained for his profession."

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Chappell has previously detailed the concentration methods that allowed him to effectively switch on and off as a batsman throughout a record-breaking career that keeps him in the conversation as Australia's finest since Bradman.

As a selector and national talent manager across the past decade he has witnessed from close quarters the evolution of Smith, who he believes always possessed an insatiable hunger for batting but improved dramatically due to his mental development and experience on the international scene.

"His mind sets him apart," Chappell says. "His ability to focus. His ability to work out bowlers and make runs in any conditions against any attack.

"He picks up the cues and clues better than anyone else. He's a better decision-maker than most, he's got a hunger that comes from somewhere and has always been there, and he's developed his game through his Test career according to his experiences."

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Across a six-year period in which he has piled on 26 Test hundreds so far, Smith's habitual fidgets and theatrical leaves have only increased, while the trigger movement as he prepares to play the ball has become more exaggerated. Those traits have earned him a reputation of being unorthodox, one that Chappell believes is inaccurate.

"I watch batsmen at the point of (the bowler's) release – I don't care what happens before then – and Smith's idiosyncrasies disguise his orthodoxy," he explains.

"Forget all the pre-movements – the dusting the pads, the touching the box – that's all just window dressing.

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"Whether it's something that just happens or whether it's something he quite happily developed because it may distract bowlers, it doesn't really matter; what matters is he gets into good positions at point of release and point of contact.

"They're the same positions that all the players who have averaged 50 and above in Test cricket have gotten into. I don't think you could make the runs he has made by being as unorthodox as I've heard him described."

Meanwhile, as Smith races up Australia's Test run-scorers list, the place of Chappell within that group excludes his record in the 'Super Test' era between 1977-79 as well as the World XI 'Tests' against Australia in 1971-72.

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Both series are feted as having produced some of the best and fiercest cricket in history, and Chappell (whose record with those inclusions would read 8,950 runs at 55.59) feels it is time they were recorded as official Tests.

"I think they're all part of one career and they should all count together," he added. "As far as I'm concerned I've got 31 Test hundreds and 8,900 runs at 55 or whatever.

"It's not something I lie awake thinking about at night but it is hard to understand the intransigence that still exists in some quarters with regards to those records."

In 2015, Cricket Australia officially recognised the World Series Super Tests statistics in a category of its own, though that move was not replicated by other national boards, nor the International Cricket Council.

Domain Test Series v New Zealand

Australia squad: David Warner, Joe Burns, Marnus Labuschagne, Steve Smith, Matthew Wade, Travis Head, Tim Paine (c, wk), Pat Cummins, Mitch Starc, Nathan Lyon, James Pattinson, Michael Neser, Mitch Swepson

New Zealand: Todd Astle, Tom Blundell, Trent Boult, Colin de Grandhomme, Matt Henry, Kyle Jamieson, Tom Latham, Henry Nicholls, Jeet Raval, Mitchell Santner, Tim Southee, Ross Taylor, BJ Watling, Neil Wagner, Kane Williamson (c)

First Test: Australia won by 296 runs in Perth

Second Test: December 26-30, MCG (Seven, Fox & Kayo)

Third Test: January 3-7, SCG (Seven, Fox & Kayo)