Quick count in my two worlds - Riley 18 games into regular season; Moonlight Graham just started preseason.
MG - last draft 52 22-yr-olds went unsigned. 43 showed up in this season's minor league pool. That's 9 who never made it to pro ball.
Riley - last draft 33 22-yr-olds went unsigned. 25 showed up in this season's minors. So 8 went elsewhere.
I might guess those are the guys who were considering pro football, basketball, hockey.