So a player's body of work from age 17 to 21 should define him for the rest of his career..lol. The minors are about finding yourself. You work on mechanics, your approach, you mentally learn the how to handle the game. I remember AA talking about Sanchez making some minor mechanical changes at Buffalo at the end of June before he ever came up. After that Sanchez had 2 starts where he was better and 2 relief appearances and then was called up.
You can try and teach a kid to throw a pitch, but you can't teach a kid to throw the ball 99 miles an hour with movement. Players progress their games at different rates. If you can only look at stats, I'm sure many of you would have advised trading Jeter when at the age of 21 his offensive numbers dipped and he committed 29 errors in the minors.