re: If your First Round pick was RB and he averaged

David Johnson averages 1,060 yards and 9.6 TDs from scrimmage per season in his entire career. That's including a 1 game season, and pretty much two half seasons (came on late his rookie year and hurt midseason last year)

David Johnson averages over 10 fabtasy points in standard per game (and his value goes way up in ppr) for his career including all of the games he did not play.