A knuckleball is a baseball pitch thrown with the fingernails against the seams of the baseball (so named because the batter can see the pitcher's knuckles as the ball is thrown, not because the knuckles are against the ball) so as to minimize backspin. A ball thrown in this manner travels at low speed and darts unpredictably, making it very difficult to hit.
The pitch is easy to learn but more difficult to master; Hall of Fame pitchers Hoyt Wilhelm and Phil Niekro utilized it to great success, as did Niekro's brother, Joe, and Black Soxer Eddie Cicotte. One of the pitch's advantages is that is not hard on the arm and some pitchers (such as Jim Bouton) have had some success as knuckleballers after losing their more traditional stuff. This also means pitchers can throw more innings than orthodox pitchers, and tend to have greater longevity, with some knuckleballers effective well into their forties. During the 1945 season, with talent depleted by call-ups to fight in World War 2, the Washington Senators had a pitching rotation which included four knuckleball pitchers Dutch Leonard (36 years old), Johnny Niggeling (41), Mickey "Itsy Bitsy" Haefner (32) and Roger Wolff, who combined for 60 complete games and 60 wins, carrying the Senators to second place.
The only three current knuckleball pitchers in the majors are Tim Wakefield of the Boston Red Sox and Steve Sparks of the Arizona Diamondbacks (as of 01/01/04). There is also a good chance that Charlie Zink who is in the Boston Organization will debut in 2004