“Moran’s Strategy in ‘Percentage’ Baseball” (Headline). “Moran is strong for this percentage baseball and hopes to be able to manipulate his pitching on this basis.” Evening Ledger [Philadelphia], April 20, 1915, p12
“Pat Moran’s System of Percentage Baseball—Race for Pennant About Over. Pat Moran Another Frank Selee in Playing Percentage Baseball” (Headline). “Selee, who built that team was the greatest percentage manager who ever handle a major league team. He was always looking ahead, and played the game according to percentage all the time.” Evening Ledger [Philadelphia], September 24, 1915, p12
“Moran has played ‘percentage baseball’ all summer. He has given much thought to his task, has figured out the chances for and against every move he has made, before he decided upon the move.” The Pittsburgh Press, October 3, 1915, p2
- NOTE: The April story, about Phillies manager Pat Moran, refers specifically to him not using his best pitchers against the other team’s best pitcher. The September story notes that Moran learned about playing the percentages while playing for Frank Selee. Selee managed Moran at Boston in the National League 1901 and was the architect of the Cubs team Moran played for from 1906 to 1909. The next occurrences of the term that I found were in 1919, again in reference to Moran, a pennant-winning manager for the second time (with Cincinnati.) (Ken Liss)
Previous earliest use (Dickson Baseball Dictionary, 3rd edition, 2009):
1ST USE. 1932 (Baseball Magazine, October, p. 496; Edward J. Nichols).