This season, not one knuckleball has been thrown.
In 2018, only one pitcher threw it — Steven Wright. His nickname is “Knucksie.” He threw 824 pitches. Of them, 719 or 87.3% were knuckleballs. This season, he has yet to play because of an 80-game suspension.
In 2017, three pitchers threw them: R. A. Dickey, Steven Wright, and Erick Aybar, with Dickey throwing the most — 2,333.
In an article on NPR’s website, physicist Alan Nathan describes how a knuckleball is thrown.
The ball has to be gripped with two (carefully manicured) fingernails and sort of pushed toward the plate. The object is to put just a little spin on it and let it be nudged around as air flows over the ball’s stitches and any little scrapes or abrasions on the leather.
The article also contains an image of “the knuckleball grip used by Boston Red Sox pitcher Steven Wright.”
Though the knuckleball has brought renown to Hall of Famer Hoyt Wilhelm and others, it’s almost extinct today in the major leagues, replaced by the knuckle curve, an offshoot of the knuckleball. Wilhelm threw his first pitch in Major League Baseball on April 18, 1952 when he was 28 years old, his career lasting until July 21, 1972.
Dan Rozenson, in a Baseball Prospectus article, describes how a knuckle curve is gripped and includes this image.
In a Sports Illustrated article, Gerrit Cole’s knuckle curveball is described as “filthy.” Watch it in action:
This season, as of May 15, 51 pitchers have thrown at least one knuckle curve though eight have thrown just one. Among the pitchers who throw it are Zach Godley, Aaron Nola, and Drew Pomeranz. In 2019, all three have already thrown more than 200 with Godley throwing the most: 48.2% of all the pitches that he has thrown have been knuckle curves, which is the most in MLB: Statcast Search | baseballsavant.com. Of his 341 knuckle curves — out of 708 pitches, batters got 18 hits (5.3%), the lowest percent of the top three, Statcast Search | baseballsavant.com. With his other 367 pitches, batters got 26 hits (7.1%), so he has been somewhat more effective when throwing the knuckle curve.
Last season’s knuckle curve leader, Lance McCullers Jr. (982, 46.6%), has yet to play in 2019 because of Tommy John surgery.
Though to some it seems like a hard pitch to hit, in 2019 batters are hitting .234 (191 for 817) off knuckle curves — Statcast Search | baseballsavant.com — but only .213 (2474 for 11603) against the other breaking pitches (slider, curveball, knuckleball, Eephus) and .217 (1221 for 5616) against off-speed pitches. On the plus side, the league average against fastballs is .266 (6266 for 23533).
Godley’s focus on the knuckle curve has not seemed to benefit him. His 2019 ERA is 7.65 (highest in his career) in 37.2 innings though his fielders must assume some responsibility as his FIP is 5.66, almost two points fewer, and his Contact Percentage is 75.3%, the highest in his career, according to FanGraphs.
Three teams have thrown only one knuckle curve this season: Pirates, Rays, and Braves. Together, they have thrown 18,302 pitches. The Diamondbacks have thrown the most knuckle curves: 526.