Castleberry has worked with Leonard as a Spurs staffer and played with Leonard in high school and at San Diego State, where he was a walk-on.
Leonard can test free agency in the summer of 2019, so Raptors president of basketball operations Masai Ujiri took significant risk with the transaction. Ujiri made the deal with a determination that he can convince Leonard to re-sign with the Raptors next summer in free agency, sources told ESPN's Adrian Wojnarowski.
Hiring Castleberry certainly won't hurt Toronto's chances of keeping Leonard.
The Raptors would be able to offer Leonard a five-year, $190 million contract next summer. If Leonard leaves the Raptors, he could sign a four-year, $141 million deal with a team with the available salary-cap space.