It is up to the discretion of officials about when to stop play for an injured player – be careful it isn’t too early, or too late.
There is not a published set of guidelines about how or when to kill a play when there is an injured player. The rules book states, “A player who has been injured to the extent that the coach or any other bench personnel is beckoned and comes onto the court shall be directed to leave the game, unless a time-out is requested by, and granted to, his/her team and the situation can be corrected by the end of the timeout.” (UPDATE: Rule 5-8-2, note does give guidelines)
Another place to find information about how to handle injured players is the case book, however, only one of the 4 plays say anything about officials stopping play, and then it only states, “the official properly halted play.” So, what should we think about before we stop the play due to an injured player.
Don’t be too late – Don’t be too early.
If a player is injured, and he/she is on the floor in the middle of play, kill the action immediately! The last thing you want to have happen is for the player to stepped on while they are already injured on the floor. If the player is in immediate danger of further injury, you will not have any problems from anyone for stopping the play.
However, if the player from team A is injured in the backcourt, and team A is on a break to their basket, it is typically a good idea to let the play continue until possession changes. That being said, we are on a slippery slope when we leave players on the floor injured. If the player is seriously injured, stop the play immediately. If they are ok until the possession is over, then stay with the player until an appropriate time to stop the play. It is a good idea to err on the side of stopping play, rather than leaving an injured player on the floor any longer than necessary.
This video is a good example of a time when the play could have been allowed to continue for a few seconds longer. Yes, the player was injured. Trail stayed with the injured player. However, his team was on a fast break that was ended at at odd time. Either stop the play immediately on a hard fall like this, or let the fast break come to an end before stopping play.
When does the player have to leave game?
Only if the coach or any other bench personnel is beckoned, and comes onto the court. In the following video, it is unclear if any bench personnel comes on the court. However, the officials do end up asking the injured player to leave the game. It is important to know this part of the procedure so that it is accurately administered.