Inside Baseball

The term “inside baseball” originated in baseball of the 1890s, meaning strategic and scientific baseball involving smart coaching and teamwork. “Inside baseball” became such a popular term that it was used in other professions, such as science and politics.
 
In politics, the term “inside baseball” means technical matters that the public is not necessarily interested in, such some overly complicated campaign finance procedures. “Inside baseball” has been used in politics since at least 1968. The Newspaper Enterprise Association’s political writer, Bruce Biossat, used “inside baseball” in 1969, 1971 and 1972 columns and was one of the first political columnists to popularly mention the term.
     
       
Wikipedia: Inside baseball (metaphor)
“Inside baseball” describes details or minutia of a subject so detailed or requiring such a specific knowledge about what is being discussed that they generally are not well known or appreciated by outsiders. The usage reflects the 1890s expression “Inside Baseball”, a forerunner of the later small ball.
 
Typically the term comes up around discussions, of science, technology, entertainment, politics, or related subjects the public has a general knowledge of, but whose inner workings are not necessary to understanding the concept as a whole.
 
An example may be a film critic’s review of a movie using insider jargon, information, or understanding of which regular movie goers would have little knowledge or even interest. Citing the director’s previous themes expressed in their movies in relation to the one being reviewed because of the director’s fascination with a particular school of film making, etc.
 
Wikipedia: Inside Baseball (strategy)
Inside Baseball is a strategy in baseball developed by the 19th-century Baltimore Orioles team and promoted by John McGraw. In his book, My Thirty Years of Baseball, McGraw credits the development of the “inside baseball” to manager Ned Hanlon. In the 1890s, this kind of play was referred to as “Oriole baseball” or “Baltimore baseball”.
 
Another team praised for their inside baseball was Chicago Cubs.
 
Wiktionary: inside baseball
Noun
inside baseball
(uncountable)
1.(idiomatic, US, sports) Technical matters concerning baseball not apparent to spectators.
2.(idiomatic, US) Matters of interest only to insiders.
 
Google News Archive
5 February 1968, Newburgh (NY) Evening News, “Brouhaha with the Press” by Jack W. Germond (Gannett News Service), pg. 6A, col. 2:
WASHINGTON—One thing almost guaranteed to happen in the New Hampshire primary campaign is gthat Gov. George W. Romney will become involved in a brouhaha with the press.
(...)
These conflicts usually are just so much inside baseball, without genuine significance in the campaign. 
 
Google News Archive
16 July 1969, Sumter (SC) Daily Item, “President Believes In Some Seclusion” by Bruce Biossat (NEA Washington Correspondent), pg. 6B, col. 4:
Today the difficulties herein described may be classified as “inside baseball.” They will stir the public the first time they seriously mess up any decision of broad popular interest.
 
Google News Archive
29 April 1971, Nashua (NH) Telegraph, “Don’t Sell Big Ed Muskie Short” by Bruce Biossat, pg. 17, cols. 1-2:
WASHINGTON (NEA)—In his present difficulties, Big Ed Muskie may be haunted by the trials of Republican George Romney in 1967.
(...)
TO OUTSIDERS, this organizational stuff is inside baseball—but it is important.
 
Google News Archive
17 August 1972, Hendersonville (NC) Times-News, “McGovern In Trouble” by Bruce Biossat, pg. 2, col. 6:
Some of their complaints have to do with the intricacies of political utterance and maneuver—what some would describe simply as “inside baseball.” It is being argued, therefore, that a lot of this stuff will wash away, never really registering with the voters.
 
Time magazine
Milestones, Jun. 10, 1974
Monday, June 10, 1974
Died. Bruce Biossat, 64, political reporter and columnist for the Newspaper Enterprise Association whose words appeared in more than 400 newspapers; of a heart attack; in Washington, D.C. Respected by fellow journalists for his comprehensive knowledge of politics, Biossat drew on a wide, carefully cultivated network of sources for his reportage and weekly columns.
 
Google Books
The Boys on the Bus
By Timothy Crouse
New York, NY: Ballantine
1976
Pg. 247:
Some of the reporters had misgivings about asking the President about the press conference situation — the viewing public might be offended to see the press taking up time with an “inside baseball” type of question.
 
Google Books
Safire’s Political Dictionary
By William Safire
New York, NY: Oxford University Press
2008
Pg. 347, col. 2:
Inside Baseball Specialized or private knowledge; the minute details savored by those in the know, found boring by most others.
(...)
Red Barber, the radio broadcaster known as the voice of the Brooklyn Dodgers, said of (Pg. 348—ed.) the term, “I’ve heard ‘inside baseball’ ever since I’ve been in baseball. The idea of an inner circle, or sanctum sanctorum, goes back all the way to the days of tribal government.”