inside baseball

noun2

1. •
   (US) Technical matters concerning baseball generally not apparent or of interest to spectators.

   • Here, the game is marked by the "little things" that have come to be defined as "inside baseball". — 1993
2. •
   (US) Matters of interest only to insiders.

   • But in fact, redistricting remained very much a game of inside baseball. — 2003