I honestly think it has to do with where his weakness is..
Not alot of pitchers are comfortable attacking with fastballs up in the zone. It goes against everything they are taught about "keeping the ball down"...
How many times do you see a catcher on an 0-2 pitch raise up and put his glove up asking for the high fastball and the pitcher ethier leaves it low or throws one the catcher has to jump for..
It seems rare that a pitcher can consistently throw that good hard fastball at the shoulders to a hitter..
If I was building a hitter, and I had to give him one big flaw in his hitting, I'd pick that flaw. There's just not alot of guys that can pound you upstairs all day.
Now inside, outside, backfoot sliders etc.etc. Those ones get exploited. Holes like Sandoval's still allow you to hit .300 +...