
Coaches will get only one challenge per game, whether it is successful or unsuccessful, according to the memo. They can use it to challenge only called fouls, goaltending, basket interference and plays when the ball is knocked out of bounds, the memo says. The NBA has tested this version of the challenge system in the G League over the past two seasons.
Coaches must have a timeout remaining to use a challenge. The team must call a timeout immediately after the event it would like to challenge, and the coach must "twirl his/her index finger toward the referees" to signal for the challenge, the memo states. If the challenge is successful, the team retains the timeout it used to stop play. If the challenge is unsuccessful, it loses that timeout.