Nova was not a top prospect, neither was GGBG. Cano wasn't highly thought of until he stuck at the big league level.
Maybe it's the ability to learn without the pressure that comes with hype. Maybe it's that some players have skill sets that translate to MLB better than the raw talent that makes a Hughes or a Joba a top draft pick.
Either way, I can't wait to see David Phelps on the mound as a member of the rotation.