[3][4] Joo began playing basketball in elementary school but was not considered an outstanding prospect due to his height and slight frame.

[5] He went on to Donga High School, one the best known basketball programs in the south, and led them to win their first national tournament in six years.

[6] Joo was recruited by Korea University but his college career was largely uneventful as his more senior teammates Hyun Joo-yup and Shin Ki-sung were the center of attention.

Joo shocked the college basketball world by dropping out during his sophomore year to sign with a professional team.

[7] Despite his domestic successes, Joo was often overlooked by the likes of Lee Sang-min, Shin Ki-sung, Kim Seung-hyun and then youngster Yang Dong-geun during national team selection.

[11][12] Joo's playing career coincided with what has been dubbed as the KBL's "golden era" of guards and he was often overlooked due to his lack of "flashy" skills.