, only about 70 Major League Baseball pitchers have regularly used the knuckleball during their careers, and its use has become rarer over time. This can be attributed to a variety of factors. The first is
selection bias in
scouting. Because the speed of any prospect's pitch is one of the quickest and easiest metrics in judging the skill of the prospect, the knuckleball, which is thrown slower than any other pitch, gets overlooked.
Tim Wakefield argued that "The problem is that [baseball] is so radar gun-oriented." Former knuckleballer and pitching coach
Charlie Hough says that the increased rarity of the knuckleball is due to scouts increasingly looking only for the best arm. This effect is increasing over time as the modern game continues to emphasize power in pitching and average pitch speed increases.
Hoyt Wilhelm,
Phil Niekro, and
Jesse Haines, three pitchers who primarily relied on the knuckleball, have been inducted into the
Baseball Hall of Fame.
Ted Lyons, another member of the Hall of Fame, relied heavily on the knuckleball after injuring his arm in 1931. Niekro was given the nickname "Knucksie" during his career. Other prominent knuckleball pitchers have included
Joe Niekro (Phil's brother),
Charlie Hough,
Dave Jolly,
Ben Flowers,
Wilbur Wood,
Barney Schultz,
Tom Candiotti,
Bob Purkey,
Steve Sparks,
Eddie Rommel, Tim Wakefield,
Steven Wright, and
R. A. Dickey. In the 1945 season, with talent depleted by call-ups to fight in World War II, the
Washington Senators had a pitching rotation which included four knuckleball pitchers (
Dutch Leonard,
Johnny Niggeling,
Mickey "Itsy Bitsy" Haefner, and
Roger Wolff) who combined for 60 complete
games and 60 wins, carrying the Senators to second place. Hall of Fame pitcher
Bob Gibson said he threw a knuckleball in practice, and that one time in a game he used it to get
Hank Aaron out. In November 2008, 16-year-old knuckleballer
Eri Yoshida was drafted as the first woman ever to play in Japanese professional baseball for the Kobe 9 Cruise of the
Kansai Independent Baseball League. In March 2010, she trained with Tim Wakefield at the
Boston Red Sox minor-league training facility. In April 2010, she signed with the
Chico Outlaws, debuting in May 2010. Another factor contributing to the rarity of the knuckleball is the difficulty of throwing it.
R. A. Dickey estimates that it takes at least a year to grasp its fundamentals. The knuckleball is radically different from any other pitch in a pitcher's arsenal, being less predictable and difficult to control. It is for this reason that the knuckleball is widely regarded as unreliable, and knuckleball pitchers are prone to extended slumps, such as when Tim Wakefield was released from the Pirates in a mid-career slump during spring training in 1995. Perhaps as a result, knuckleball pitchers often view themselves as members of an exclusive club, with its own
uniform number (49, first worn by Wilhelm) and leader, Phil Niekro, whom
The New Yorker in 2004 called "the undisputed Grand Poobah" of the group after Wilhelm's death. Because they cannot discuss pitching with non knuckleball-using teammates, they often share tips and insights even if on competing teams, and believe that they have a responsibility to help younger players develop the pitch. In 2012, when R. A. Dickey became the first
Cy Young Award-winning knuckleball pitcher, he called the award "a victory for … the knuckleball fraternity", and of the dozens of phone calls he received after the announcement, Niekro's was the only one he answered. When originally developed, the knuckleball was used by a number of pitchers as simply one pitch in their repertoire, usually as part of changing speeds from their
fastball. It is almost never used in a mixed repertoire today, and some believe that to throw the knuckleball effectively with some semblance of control over the pitch, one must throw it more or less exclusively. At the same time, pitchers rarely focus on the knuckleball if they have reasonable skill with more standard pitches. Unlike conventional pitches, which perform fast results without much exertion, a knuckleball pitcher must train his body and muscle memory to be able to execute a 65 mph pitch with less than one rotation. On June 24, 2023, the
San Diego Padres called up
Matt Waldron to start against the
Washington Nationals. This makes him the most recent and only active knuckleballer in Major League Baseball. Prior to Waldron,
Steven Wright of the
Boston Red Sox was considered to be the last active knuckleballer in the MLB; he has since been released from the team.
Mickey Jannis, prior player of the
Baltimore Orioles organization, also throws the knuckleball, and made his major league debut on June 23, 2021. Among
position players making pitching appearances, those who have utilized the knuckleball include
Wade Boggs,
Danny Worth,
Alex Blandino, and
Ernie Clement. On October 1, 2023, pitcher
George Kirby of the
Seattle Mariners threw his first knuckleball in an MLB game, drawing a swing and miss from the
Texas Rangers'
Corey Seager. After the game, Kirby confirmed that he chose this day to debut the pitch as a tribute to
Boston Red Sox knuckleballer and World Series champion
Tim Wakefield, who had died that morning. ==Use in pitching==