Bouton's frequent use by the Yankees during these years (he led the league with 37 starts in 1964 in addition to pitching in that year's World Series) probably contributed to his subsequent arm troubles. In 1965, an arm injury slowed his fastball and ended his status as a pitching phenomenon. Relegated mostly to bullpen duty, Bouton began to throw the knuckleball again, in an effort to lengthen his career. By 1968, Bouton was a reliever for the minor league Seattle Angels.