Before we get carried away ... I know that players have gone to feeder clubs to improve their game. I'm restricting the focus to Brazilian players because @ issue here in the thread was the transitioning of Neymar into European football. That's why the quality of Santos came into question.
An African player who left Africa as a youngster and started professional life in Europe is differently situated from a Brazilian player who has had professional exposure in Brazil but none in Europe @club level. Same too any European player who eventually graduates to a bigger European club.
That's why I've mentioned Anderson, Pato and Kaka ... there's always this recurring notion of the next Brazilian prodigy ... Neymar seems a bit more exposed than some of the other names. So I thought having a look at the experience/background of other Brazilians before Neymar ... might be constructive.