The Kings assigned rookie guard to the Reno Bighorns of the NBA Development League on Thursday.
The Bighorns begin their season Friday at Sioux Falls.
McCallum, who traveled with the Kings to Phoenix for Wednesday night's win, has not appeared in a game during the regular season.
The move had long been expected, as the Kings want their second-round pick to develop with playing time.
Brandon Heath, DeQuan Jones and Trent Lockett were with the Kings in training camp and play for the Bighorns.
The Kings operate the Bighorns, so McCallum will be in schemes and running drills similar to what the Kings are doing.