Context changes everything
A fastball thrown after two straight breaking balls behaves differently from the same fastball thrown first. The hitter's timing has been calibrated by what came before, and a pitcher's whole craft partly consists of exploiting that calibration rather than simply owning better raw stuff.
This is why judging a pitch in isolation misses so much of what is happening. Two pitchers can throw an identical fastball at an identical velocity and get wildly different results, because one of them set it up and the other did not.
Planning the at-bat, not the pitch
Good sequencing treats an at-bat as a small story with a beginning, middle and end, rather than four or five unrelated events. Early pitches are often used to plant an idea — a location, a shape — that later pitches deliberately contradict once the hitter has adjusted to it.
That is a patient, almost theatrical approach to a contest that outsiders sometimes assume is pure power against pure reflex. It rewards a pitcher who can hold a plan under pressure as much as one who can simply throw hard.
The hitter's countermove
Hitters do not stand there hoping to guess correctly. They study tendencies — what a pitcher likes to throw in a given count, off a given prior pitch — and narrow their expectations before the ball is even released. A sequence that would fool a stranger can fail completely against someone who has done the homework.
That is the real contest inside the contest: two competing bodies of preparation, each trying to be one step ahead of the other's plan. Arena's MLB positions guide covers the roles that make this possible on the pitching side.