Casey was the top assistant to Mavs coach Rick Carlisle, who referred to him as the team's defensive coordinator. Casey, 54, has been with the Mavs for three seasons and was credited for the defensive success Dallas enjoyed this season and throughout its run in the playoffs, which ended with an NBA title.
He coached the Minnesota Timberwolves from 2005 through midway through the 2006-07 season. In his year-and-a-half stint with the Timberwolves, Casey posted a 53-69 record before he was fired on Jan. 23, 2007.
In Toronto, Casey will replace Jay Triano, who was fired at the end of the season after the Raptors posted the NBA's third-worst record at 22-60.
-- Dwain Price