You will know he's a legit pro prospect if he's drafted in the top twenty rounds. 94% of American MLBers were drafted in the first twenty rounds. 84% were drafted in the top ten rounds. Being drafted later means the player is seen most likely as single A roster filler.
Those are some pessimistic statistics (if there is such a thing). Here were are talking about how to tell whether a pre-teen is the real deal, and then we get this information. I personally think the guy helping fill out the single A roster is the real deal, especially when you start doing the math on what percentage of pre-teen players make it to the "pros". Not really bashing the post, just trying to put a good spin on making it past college. Heck, making it to college is a huge deal. I hate to think of this like climbing mountains - climb the first mountain only to see another mountain on your path. Climb that one and you get rewarded with yet another. At some point you should reach the valley and celebrate. Maybe there is another mountain in the distance, but you should get some time to revel in your success.
My son is a 2017, so we are thinking about this one. What about the kid who is not a strong college student? What if he were to get drafted in the 25th round and spent a few years in A ball? Worst case, it gives him an experience he would otherwise never get and the chance to mature. Best case, he beats the odds and makes the MLB. I look at it like joining the army, but no one is shooting at you :-)
A kid drafted late out of high school would most likely spend his first season in short season Gulf Coast League. He would be playing with other late high school picks and a lot of 16-18yo Carribean players. The second year would likely be in the regular short season league playing against high school top picks and 21 and 22yo players just out of college. If he survives he then moves on to playing low A where the average player is 22, 23 years old.
A kid from our high school signed after senior year. He was a 7th round pick. He was completely overwhelmed. He could have gone Power 5 D1. He spent three years struggling against former college players in short season before being released.
I talked with him when he was working in an academy and going to college at night. He called signing a big mistake. Since he was only 21 he hung on in the Atlantic League (Indy ball) for two years hoping to get another shot.
This kid could have played at Stanford. He felt he owed his grandmother for raising him. Maybe he would have washed out at Stanford. But he would have come away with an college education. Instead he signed for 175K out of high school.