Greening attended Montello Primary School and Parklands High as he grew up in the industrial town of Burnie in northern Tasmania.
He made his senior debut for the club the following year in a game against Hawthorn and became a regular in the side, playing as a ruck rover, half forward, centreman and wingman.
In the Magpies' round 14 (8 July) encounter with St Kilda he had suffered severe cerebral concussion as a result of a hit received during the game.
The incident took place after Greening had taken the first mark of the game, he kicked the ball towards Peter McKenna in the goal square and was floored afterwards by St Kilda player Jim O'Dea.
Greening, who was comatose for 24 hours and didn't regain full consciousness for several days, was considered lucky not to die or at least be permanently disabled.
"St Kilda's Jim O'Dea received a 10-match suspension for the incident, but Peter McKenna recalls that the initial fear as Greening's teammates ran towards their prostrate young wingman was that they would find him dead.
Subsequent to the event, the club released the following as part of its tribute:"Everything about John Greening bore the stamp of a champion – superb skills, sure hands, and an outrageous spring.