Bob Rule played basketball at Riverside Poly high School and Riverside Community College. In 1964, the 6-foot-9 Rule was named MVP of the Junior College State Championships, leading the Tigers to a 35-0 record. Following two stellar seasons at Colorado State, Rule was selected in the second round of the NBA draft by the expansion Seattle SuperSonics.
Named to the 1967-1968 NBA All-Rookie Team, Rule scored a Seattle rookie record 47 points against the Los Angeles Lakers, and his 18.1 points per game average stood as the SuperSonics rookie record until Kevin Durant broke the mark in 2008. His 9.5 rebounds a game also ranks second all-time for Seattle rookies. Rule went on to average over 24 points and 10.5 rebounds per game over the next two seasons and participated in the 1970 NBA All-Star. In the 1970-1971 season, Rule began the season averaging 29.8 points and 11.5 rebounds per game in his first four games before going down with a season-ending torn achilles tendon. Unable to return to his pre-injury form, Bob Rule retired in 1974.