Bob Gibson, a Human of the 20th century, was a professional baseball player and pitcher in Major League Baseball. In 2370, Jake Sisko had been trying to figure out how to hit Gibson's fastball in the holosuite.
Early that year, when Jake announced to his father that he had good news, his father guessed (incorrectly) that he finally figured out how to hit Gibson's fastball, second only to Jake passing his algebra test. (DS9: "The Homecoming")
In an early draft of the script, Sisko referred to Sandy Koufax rather than Gibson. [1]
According to the Star Trek Encyclopedia, 4th ed., vol. 1, p. 304, Gibson was a Hall of Fame member, who played for the St. Louis Cardinals as a pitcher from 1959 to 1975; during his career he struck out 3,117 players and won the Cy Young Award for best pitcher in 1968 and 1970.