If you describe a situation as a whole new ball game, or a different ball game, you mean that it is completely different from what came before. In Spanish we usually say “Esa es otra historia”, to express this idea.
- I’d been working as a teacher for several years, but working with little kids was a different ball game.
Note: `Ball game’ is often used in American English to refer to a game of baseball.
Really interesting. As a fan of baseball I appreciate the note!