Just Throw It Down the Middle
Is throwing a four-seam fastball down the middle a good idea? Regardless of whom you ask, the answer is probably no, and for good reason – the heart of the zone is where the majority of hard contact occurs, and fastballs are the most contact-prone of any pitch type. This disdain is rooted in our baseball lexicon, too. You’ll notice that after a ball is hit out of the park, broadcasters tend to remark that the pitcher “left one over the middle” or “hung his fastball.” The location is often to blame.
That doesn’t stop pitchers from trying, though. That’s not always because they want to – command comes and goes, after all – but it’s also because hitting a baseball is extremely difficult. Swings and misses happen! Bad contact happens! In each season since 2015, when Statcast data became public, hitters have accumulated a negative run value against down-the-middle fastballs. They’re still in the red despite seeing easier pitches. Though no pitcher would want to live solely in the middle, it makes sense why one might venture there.
But 2021 brought changes to the majors, and this is one of them: Hitters did worse against so-called meatballs than ever before. Here’s a graph that shows the league’s run value per 100 against fastballs in Baseball Savant’s “Heart” zone. Again, 2015 is the starting point:

