When legendary St. Louis Cardinals pitcher Bob Gibson was in college, he reportedly told his catchers to make whatever hand-signals they wanted before the pitch. If you held down one finger, he’d throw a fastball. If you down two fingers, he’d throw a fastball. If you held down three fingers, he’d throw a fastball. If you made the batman symbol with your hands, you’re getting a fastball.
Reflecting on his baseball career later in life, Gibson said that he enjoyed a competitive advantage by being able to cultivate his fastball strength. Other pitchers, lacking the quality of Gibson’s fastball and fixating on the idea that they needed a curveball and slider as well, used up their focus on improving their weaker pitches.