Root enters the Ashes as England's most experienced batsman, with Lyon Australia's most-capped bowler.
But their time together pre-dates both their Test careers, having played for the Prospect Pirates in Adelaide grade cricket in 2010-11 while at the Darren Lehmann Academy.
"It was a pretty special time," Lyon told AAP.
"We used to go to training early and I used to help him with off-break bowling and he used to help me with my batting.
"I think my coaching has helped him a bit more with his bowling than his coaching with my batting."
Lyon took 18 wickets that season at an average of 20.44. Root scored 353 runs at an average of 29.42.
With Lyon's help, Root also took five wickets at an average of 23.8.
Somehow, with two future world-beaters in their team, the Pirates finished 11th of 13 teams and won only two games.
It's not inconceivable to think Root could have a big role with the ball this English summer, particularly after Jack Leach's back injury ruled him out.
England called in Moeen Ali, but he himself has admitted he will not be able to hold up an end.
That potentially leaves Root as a valuable second spinning option for the England quicks to work around.
Lyon and Root remain close.
The pair were spotted in close conversation during the SCG Test last year, with Lyon again giving the star batter spinning tips.
"It is a unique story when you look at it," Lyon said.
"In my eyes he is one of the greats to play the game and what he has done for English cricket needs to be applauded.
"Our time playing grade will hold some fond memories for me for the rest of my life."
Together, their careers have also formed a common path.
Lyon made his first-class debut late in that 2010-11 season for South Australia, while Root had made his the previous winter for Yorkshire.
Lyon's Test debut came shortly after in 2011 in Sri Lanka, and Root's the following year against India in Nagpur.
Root is now England's second leading run-scorer in history and Lyon Australia's third leading wicket-taker.
In 27 Tests against each other leading into the Ashes, Lyon has removed Root seven times.
A battle that now looms as a crucial part of the 2023 series.
"Joe has been one of the best batters in international cricket for a long time now," Lyon said.
"He always provides a different challenge and is always looking to be get better."
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