Throw In - Ball at disposal of a player

[Rob1968]

"The Basketball Handbook, p.71, TABLE 3-1: Time Factors
Time Allowed for: 10. Throw-in from out of bounds 5 sec."

(Thus, if the thrower-in is not out of bounds, the 5 second count must not be started. If it is started before the thrower-in is out of bounds, the 5 second count cannot be a full/valid allotment.)

4-42-1 . . . The thrower is the player who attempts to make a throw-in.
4-42-2 . . . A throw-in is a method of putting the ball in play from out of bounds.
4-42-3 . . . The throw-in and the throw-in count begin when the ball is at the disposal of a player of the team entitled to it. (that is, entitled to make the throw-in.)
4-42-4 . . .The throw-in count ends when the ball is released by the thrower so the passed ball goes directly into the court.

9-2-4 . . .Once the throw-in starts, the ball shall be released on a pass directly into the court before five seconds have elapsed.

(Thus, the throw-in count can only be started when it is possible for the thrower to "pass the ball directly into the court," which cannot be done from a position in the court. (It is impossible to make a throw-in from in-bounds.)

Provision allowing the administering/covering official to start the count, in the event of appreciable delay on the part of the throw-in team making a player available to attempt the throw-in, appears in the OFFICIALS MANUAL 2.2.2 Throw-ins A. General Provisions . . .