Born in Terre Haute, Indiana in 1947, Hamblen graduated from Garfield High School in Terre Haute in 1965. As a Sophomore, he was a reserve guard on the 1963 IHSAA State Finals team that was defeated by South Bend Central, 72-45 in the first game of the semi-final round. He finished as the Purple Eagles' #3 scorer behind 3-time All-American Terry Dischinger and Hall of Famer Clyde Lovellette. Hamblen was recognized among the top 12 high school basketball players in Indiana and 25 years later was named to the Silver Anniversary Team in 1990 by the Indiana Sports Hall of Fame.
Hamblen graduated from Syracuse University in 1969. On the Syracuse Orange men's basketball team, Hamblen earned three letters and was team captain as a senior. Hamblen averaged 4.6 points per game as a senior.
Hamblen served as an interim head coach for two different teams – the Milwaukee Bucks in 1991–1992 and the Los Angeles Lakers in 2005. He also has served as an assistant coach on six NBA teams (Kansas City/Sacramento Kings, Milwaukee Bucks, Chicago Bulls, Los Angeles Lakers), often alongside Phil Jackson. Hamblen has been an assistant coach on seven championship teams, two with Jackson's Bulls and five with Jackson's Lakers. Jackson retired after the 2010–11 season, and Hamblen's contract with the Lakers expired as well.
Head coaching record
|Regular season||G||Games coached||W||Games won||L||Games lost||W–L %||Win–loss %|
|Playoffs||PG||Playoff games||PW||Playoff wins||PL||Playoff losses||PW–L %||Playoff win–loss %|