outfield bleachers; outfield seats
Baseball term for the seating area beyond the outfield fence. Also used figuratively for a position of non-involvement.
I caught a home run ball in the outfield bleachers.
He's always complaining from the sidelines.
Figurative use derived from the baseball sense, referring to someone not directly involved in a situation, often with a nuance of being uninformed or offering unsolicited opinions.
Please don't mind the opinions of outsiders.
He's always an onlooker in meetings.