He played for the Detroit Pistons, New York Knicks, Baltimore Bullets, Los Angeles Lakers, Cleveland Cavaliers, and San Diego / Houston Rockets of the National Basketball Association from 1961 to 1972.

[2] He was known as "Space", a nickname which alluded to "his ability to stay in the air during drives to the basket or to the length of his long-distance shots".

[5] He was traded along with Johnny Green, Jim "Bad News" Barnes and cash from the Knicks to the Baltimore Bullets for Walt Bellamy on November 1, 1965.

[7] Before the 1968–69 NBA season, the Bucks traded Egan to the Los Angeles Lakers for a future draft pick.

[8] He became a key rotation player for the Lakers, who reached the 1969 NBA Finals but were beaten by the Boston Celtics in Game 7.

[12] He was acquired by the San Diego Rockets from the Cavaliers for a third‐round pick in the 1971 NBA draft (41st overall–Jackie Ridgle) and cash on December 8, 1970.