Approximately two hundred and fifty-five players are drafted every year. Yet, a typical NFL Draft class produces only forty to fifty players who will develop into productive starters. The reality is that the majority of NFL draft picks struggle to even make an active roster or are marginal backups and are out of the league within four years. It is also a fact that about one third of the players selected in the 1st round will disappoint.
http://www.profootballdraftnetwork.com/