“They say the double-play is a baseball pitcher’s best friend in that it gets him out of many a precarious situation.” Joseph D’Adamo, Baltimore Evening Sun, April 2, 1949, p6
“A pitcher’s best friend is his infield.” (Start of a caption on two photos with text describing a pair of double plays in game between the Yankees and the A’s.” New York Daily News, May 15, 1948, p293
— This is earlier than the citation above, but doesn’t explicitly call the double play the pitcher’s best friend.
Earlier uses:
“In the course of my experience I have found that luck is a pitcher’s best friend.” Roscoe Coughlan of the Oakland Pets, quoted in Oakland Daily Evening Tribune, January 2, 1889, p6
“Walker, the Cards’ pitcher, thinks that next to a heavy-hitting teammate the sun is a pitcher’s best friend.” Atlanta Consitution, December 20, 1934, p15. (UPI story that also appeared elsewhere)
“To this day, Walter {former pitcher Walter Mails} remains a strong adherent of the ‘dust’ ball, which he describes as the pitcher’s best friend.” Prescott Sullivan, San Francisco Examiner, March 12, 1940, p21
— The dust ball, or duster, is described as a brush back pitch.
- NOTE: There are also several mentions in the 1940s of particular individual players who, because of their fielding prowess, were referred to as a pitcher’s best friend.
No earliest use given in 2009 Dickson Baseball Dictionary