The coach's challenge is relatively new to the NBA, and the league already has altered the process slightly since its debut.
You know when a controversial call happens and every person on the court starts wagging their pointer finger in a circular motion for a review? As of 2019-20, coaches can call a timeout and request a challenge on the floor.
The procedure started as a trial run. After it was met with resounding approval, the NBA elected to keep the coach's challenge for good heading into the 2020-21 season.
Ahead of the 2023-24 season, though, the NBA made changes to the number of challenges and how it affects timeouts. The Sporting News breaks down the coach's challenge rules below.
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How the NBA coach's challenge works
(Per the NBA's official 2023-24 rulebook)
- Each team is entitled to one challenge to start the game. If that first challenge is successful, coaches will be rewarded with a second one, as of the 2023-24 season.
- Coaches cannot challenge a call in the final two minutes of the fourth quarter and last two minutes of any overtime. During those minutes, only officials can trigger a review.
- A team may utilize a challenge to trigger instant replay review of only the following three events:
- (1) a called personal foul charged to its own team
- (2) a called out-of-bounds violation
- (3) a called goaltending or basket interference violation
- Any called foul, violation, or other decision by the game officials not listed above, or any non-call, is not a challengeable event.
- The on-court crew chief makes the final decisions on foul call reviews. The replay center referee makes the final decisions on all other reviews.
- Here is the wording that matters most on challenges: "Clear and conclusive visual evidence" is required in order to overturn a call on the floor.
How NBA coach's challenges affect timeouts
A coach must call a timeout to signal for a challenge on the floor.
- If the challenged call is not overturned and the challenge is deemed unsuccessful, the challenging team loses its timeout.
- If the challenged call is overturned and the challenge is deemed successful, the challenging team retains its timeout.