How do substitutions and re-entry work?

Re-entry (Rule 4, Section 5):

• Any player, starter or substitute, may be replaced and re-enter once, in the same spot in the batting order.
• A starter and her substitute can't be in the lineup at the same time.
• Re-entering a second time, or in a different batting spot, is an illegal re-entry. That player is disqualified once the other team brings it to the umpire's attention.

Reporting substitutes (Rule 4, Section 6):

• Report every substitute to the plate umpire when she enters. Also report any defensive change involving the pitcher or catcher.
• An unreported substitute is only penalized if the other team protests. Depending on when it's discovered, the penalty can include the player being called out or the play being replayed.
• You can add eligible roster players to the substitute list at any time during the game.

Injured runner: if an injury stops a runner from reaching an awarded base, a substitute may take her place. In JO pool play, any player may replace the injured player.