When I used the term "measureable" earlier, I should have been more precise.
I was referring to the particular measurables pertaining to physically dominant size and frame that no amount of dedication or determination will allow a normal-sized person to overcome.
One time a military basketball team I was on played a charity game against a team consisting of five members of the then-Super Bowl champion New York Giants. Until that night, I thought rebounding was 90% desire. But after being in the vicinity of a couple loose balls that Pepper Johnson wanted, I quickly realized that my effort, desire, hustle, timing, and technique totaled up to 0% relevance if Pepper decided he wanted the rebound.
One of my rebound attempts produced one of the most terrifying moments of my life. One of our guys clanged one off the rim that hung in the air long enough for me to evade Pepper's box out and take the three giant steps required to circumnavigate his rear end. As I lunged toward the ball, I accidentally poked Pepper in the eye. For a split second, a look of rage crossed his face and I thought, "Oh no. He's going to kill me right here in front of my whole family and two thousand witnesses!" Fortunately, his professional demeanor asserted itself and the look of rage dissipated as quickly as it had come. Instead of killing me, he took the ball, which he had been effortlessly palming in his right hand after winning the rebound, and fired a strike the length of the court to Stephen Baker the Touchdown Maker for an uncontested layup.
Football and basketball quickly teach non-prospects it is not safe for them to be on the same field or court as the real prospects.
For some reason, having a fastball blown by you doesn't produce the same kind of significant emotional event as leaving a court grateful that a giant spared your life. You walk away thinking, "Yeah, I could learn to hit that" even if there's no way you ever could.
On my D3 college football team, I never heard any teammate express any hope or dream of playing in the NFL. Not once. Ever. We all knew better. We had all had our butts kicked too thoroughly too many times by players who themselves were not prospects to even imagine we could overcome the physical differences.
However, nearly every college baseball team in every division and classification has several players, sometimes many or even a majority of players, who ignore ample evidence to the contrary and continue to believe their hard work will one day pay off with an opportunity to play pro ball.
And the proportion of baseball players with unrealistic dreams is even higher in high school, and higher still among middle school rec players.