Under Rule 11.1, for all accidental deflections, including when the ball hits the player or opponent or their equipment or caddies:
There will be no penalty and the ball will be played as it lies (with limited exceptions).
To address any concern that a player might deliberately position equipment to act as a backstop and potentially deflect his or her ball, there will be a penalty if the ball hits equipment that was positioned for that purpose (Rule 11.2a).
Reason Behind Change
Many objects, persons and animals are present on a golf course during play; it is inevitable that a ball in motion will sometimes hit them before coming to rest, and a player is generally required to accept the outcome (whether good or bad).
Just as there is no penalty in stroke play if one player (or his or her equipment or caddie) accidentally deflects another player’s ball, there is no need for a penalty when a player (or the player’s equipment or caddie) accidentally deflects his or her own ball.
The outcome in such cases is random and unpredictable, and it results in a disadvantage for the player at least as often as it results in an advantage.