Skin in the game. To have skin in the game is to carry a risk yourself, in money or otherwise, because you are involved in the goal. The phrase is often credited to Warren Buffett. William Safire disputed this and pointed to earlier uses. The earliest citation in the Oxford English Dictionary is from 1976.
Hero or goat. In sports, the goat is the player whose mistake is blamed for the loss. Merriam-Webster gives the example: “In the last inning, a home run can make you the hero, and a strikeout can make you the goat.”
Monday morning quarterback. This is someone who second-guesses. The phrase comes from a fan’s critical review of the weekend’s football game. Merriam-Webster dates it to 1931.