NBA.com - RULE NO. 9-FREE THROW
Section II-Shooting of Free Throw
a. The free throw(s) awarded because of a personal foul shall be attempted by the offended player.
EXCEPTIONS:
(1) If the offended player is injured or is ejected from the game and cannot attempt the awarded free throw(s), the opposing coach shall select, from his opponent's bench, the player who will replace the injured player. That player will attempt the free throw(s) and the injured player will not be permitted to re-enter the game. The substitute must remain in the game until the next dead ball.