Personally, I believe that the over reliance on the first few years of grade is what flaws your argument.
Tim Smith is a good example here. He was rookie of the year one year. And then basically fell off the radar. Conversely, Kieran Foran was not rookie of the year, and look at him now. Then you've got the fact, that backs will always be ready for grade before forwards (with a few notable exceptions). When was the last time that a forward was rookie of the year? Not even Sonny Bill was rookie of the year. And that says something.
Then you've got, what I'll call the "Bryan Fletcher factor"....usually forwards...who develop later perhaps from good players to great players once they hit 24,25.....Should the roosters (he was a paddo colts jr and as such, roosters can actually lay claim) be disadvantaged by the fact that he developed later? Terry Campese is another good example of this.
Secondly, the words "junior development" are inaccurate in the modern day. "junior scouting and recruitment" is far more applicable....You have kids from QLD and NZ playing in the NYC for Sydney clubs..Kids from the south coast of NSW playing for Nth Qld and so on...They haven't developed the juniors. Rather they've scouted the best juniors.
The other problem lies in the disproportionate numbers of local juniors and how many actually go on to play grade. Penrith, Parramatta and St George Illawarra have massive nurseries, not via the work of the clubs themselves, but rather by the numbers of junior kids they have playing in the junior competition. If the majority of local juniors don't come from these comps in NSW then there's something amiss.
Yet even these clubs are recruiting from outside their area. Tim Smith and Michael Witt are once again great examples. Qld boys playing for Parramatta. Steve Price from Toowoomba playing for the dogs. Sonny Bill Williams and Roy Asotasi from NZ to playing for the dogs, and then there's Benji..... Why? Because they want to win. And fair enough too. It's not good enough to have the best local juniors playing for you these days. These days you need the best juniors. And given that you've got 3 clubs in QLD, and superclubs in Western Sydney, and the Illawarra, then it's likely that there are going to be more talented players out there, via weight of sheer numbers........
The days of the "development of the local junior" are over.....And the development of the "junior" needs to be assessed over an entire career, not simply whether they play a game, or even a season, of first grade....
