Nature versus nurture; such is the general explanation offered when consideration turns to the simultaneous rise of Lionel Messi and Cristiano Ronaldo.
The prodigious talent and the relentless grafter. An unsatisfying theory in places, a quick assessment of their contrasting physiques suggests there is some truth to it nonetheless.
When compared to the 18 year old who made his Manchester United debut in 2003, the Ballon D'Ór winner who left for Real Madrid six years later was a different specimen altogether.
Although natural ability is crucial to Ronaldo's own success, the increasingly intensive manner in which he approached his physical preparation coincided with an enhanced ability to harness those raw materials - for Messi, it has never seemed as intrinsic.
While stories of his commitment and attitude at Manchester United have become constants in the stories of former United players on the pundit circuit, former United fitness coach Walter Di Salvio has revealed yet another astonishing example of the Portuguese's determination to improve.
Speaking to Paul Condo, Di Salvio discussed a particular habit of Ronaldo's that is indicative of his work-ethic:
While his team-mates went in for their showers, he went out to the back of the complex, where it borders on a patch of woodland, so that he could practice his ball control in difficult conditions.
In the woodland undergrowth the terrain was very uneven, full of exposed tree roots, and Ronaldo would kick the ball hard into that area and chase after it, trying to bring the unpredictable bounces under control.
While Alex Ferguson may not have been too happy with the idea of Ronaldo doing some unnecessary damage to himself out in the woods, one begins to understand why he dubbed Ronaldo the 'most gifted player' he ever managed.