Just the right spin and speed to resolve a split. Starting at just the right drop point at your end of the alley. Each split has it's own characteristics.
Just the right spin and speed to get a strike in the first place.
Then take into account your own physical tendancies. I used to pull to the left when I'd get tired....which required adjustments in technique late in the game.
All that kind of stuff.
Just like pitching isn't just "throwing" a ball.
Obviously you haven’t seen the Red Sox bullpen this year.