A player saving the ball in the air can ask for, and be granted, a timeout even if that player is going out of bounds. The key is whether, or not, the player has control of the ball.
5-8: Time-out occurs and the clock, if running, shall be stopped when an official: Grants a player’s/head coach’s oral or visual request for a time-out, such request being granted only when: The ball is at the disposal or in control of a player of his/her team.
5.8.3 SITUATION D: A1 or A2 requests a time-out: (a) while airborne A1 is
holding the ball; (b) while A1’s throw-in is in flight toward A2; or (c) when the ball
is on the floor at A1’s disposal for a throw-in. RULING: The request is granted in
(a) and (c), but denied in (b), as there is no player control while the ball is loose
between players.