Hi Don! A quick note on “pinch hitting”
You’re allowed to send players not currently in the lineup to the plate instead of players in the lineup. It’s called “pinch-hitting”. For example, if you have an absolutely horrible right-handed hitter (except that he doesn’t hit) up against a right-handed pitcher in a situation where failing to get on base probably ends the game, and you have one (or more!) good left-handed hitters on the bench, you can “pinch-hit” for the right-hander and increase your chances to win.
Check it out! It’s in the rule book and everything.