Aroldis Chapman is known primarily for one thing, his fastball. One of the most electric pitches in all of baseball, it has averaged an eye-popping 99.9 miles per hour over the course of his Major League career. It is his bread and butter as he has thrown it 79.8 percent of the time. However, having crossed onto the wrong side of thirty earlier this year, will Chapman continue to be able to blow hitters away with his overpowering fastball for the rest of career?
The Aging Curve
The below graph shows relievers aging curves as developed by Bill Petti and Jeff Zimmerman of FanGraphs. The data was gathered from the 2002-2011 seasons, but can still be applied to this situation. It can be seen that relievers tend to lose about three miles per hour of the velocity from the beginning of their careers to the time they are in their late-30s.
So as the years go by, one might expect Chapman’s velocity to slowly decline. By the above aging curve, chances are he only bottoms out at about 96-97 miles per hour. However, Major League hitters are capable of hitting those pitches. That is even more prevalent due to the rise in average velocity, so hitters are now better equipped at handling higher-speed fastballs.
Location, Location, Location
Furthermore, it appears as if Chapman is not hugely reliant on location.
It can be seen that over the course of his career, most of his fastballs have been in the middle of the zone. Again, Major League hitters will do damage with these pitches, but the sheer velocity that Chapman currently possesses allows him to circumvent this dilemma.
He also has a decent amount of rise to his fastball. Of course, when you’re throwing 100-plus miles per hour up in the zone, it is hard to layoff as a hitter. In his career, Chapman has gotten 31.3 percent swings on pitches out of the zone. The average across the MLB in 2017 was 29.9 percent. So he’s able to generate a few more out-of-the-zone swings. However, if his velocity decreases even slightly, it could open the door to batters being able to see the ball better and perhaps lay off those high pitches out of the zone.
In terms of overall contact against his fastball, the number is 67.5 percent in his career. In 2017, hitters made contact on 77.5 percent of their swings. So at the moment, they can’t catch up as much, but the same logic above applies if he experiences a slight decrease in velocity.
There are many more metrics one could look at. But in general, it would seem as if it would be beneficial for Chapman to continue to develop his slider even more, and even work on incorporating his seldom-seen changeup as he gets deeper into his career.