There is often a big gap between being good against other schoolboys and junior reps and being able to cut it against the monsters that generally filter into the NRL. As Malla mentioned, the current system has a tendency to let some talent fall through the cracks because if by 21 they're not physically developed, they often find themselves in a position where the paid contracts dry up and they're forced into other jobs to pay the rent.
In part I see that as a really big issue for the ongoing ability for the NRL to keep producing the best players. I look at a player like Curtis Rona who didn't quite break into the NRL by 21 that was forced to club hop for a few years before having a breakout season at 23yo. Going back a bit I recall seeing Paul Rauhihi having fulfilled a role as a modestly paid reserve grade player until he signed with us at 26 or 27 years of age by which stage he'd become a very good player. I'd assume that players like them might be more common if the NRL saw fit to implement a system where the risk of playing semi professional football was balanced financially with the fact that even in the reserve grades you can still cop very serious injuries. I'm sure that some potentially great talent has walked away from the game because if you haven't made it by a certain age, the financial incentives are gone and it's probably easier to just play as a hobby when you have to work full time to pay the bills.
