Player prop and a player who doesn't play

MLB's rulebook decides what happens to the game; it says nothing about wagers. What happens to a bet is set by each sportsbook's own house rules, and they genuinely differ from book to book. Check the house rules of the book where the wager was placed. A prop on a player who never appears cannot lose on the field, so each book defines what counts as an appearance — one pitch? a plate appearance? announced in the lineup? — and those definitions, plus the treatment of partial appearances, differ by book.

Lineup choices are a team matter; the rulebook is silent. Whether a prop on a player who never appears is cancelled is entirely up to each book.

• What counts as an appearance for hitter props — a plate appearance, a pitch faced, a defensive inning?
• Is a player who enters as a pinch runner or defensive replacement treated as having appeared?
• How are same-game parlay legs repriced when one leg voids?

Posterior is verifying each major book’s current house rules for this scenario and will publish per-book answers with sources and check dates. We do not state a book’s policy until we have read it.