Betty by Gary Delainey and Gerry Rasmussen for May 06, 2023

I hope the coach is Lucy Van Pelt. She could tell you about playing outfield.

Chewing tobacco.

Not a good idea to put your phone there. You might slide into something on your bottom and break it.

That’s a good question. Why put pockets on a baseball uniform? The bat is too big and the pine tar goes on your neck :D

Prophylactics

I recall ballplayers that kept “baserunning gloves” in that pocket…

And interestingly, today’s “Big Nate: First Class” also addresses what “Ballplayers” might keep in that pocket.

Tins of chaw

Chewing tobacco is my guess. (In the early years.)

I literally had to keep my wallet in mine when I played. Only place to keep my money to buy after game refreshments.

Batting gloves in one and running gloves in the other.

The pocket(s) may have been used to hold a handkerchief, back in the day. Or to hold one’s cap, when it was not being worn. Or chewing tobacco, as some have already said.