After playing his rookie season with the Celtics (1954–1955), Ramsey spent one year in the military before rejoining the team. In the eight seasons he played after military service, he was a member of seven championship teams (1957, 1959–1964). He was a major contributor of the Celtics dynasty, playing behind the duo of Bob Cousy and Bill Sharman and playing with Bill Russell, Sam Jones, K. C. Jones, Tom Heinsohn, John Havlicek and Satch Sanders. In his 623 NBA games Ramsey scored 8378 points for an average of 13.4 points per game. He was inducted into the Naismith Memorial Basketball Hall of Fame in 1981. His #23 is retired by the Celtics. Ramsey's best statistical season was 1957–1958; he averaged 16.5 points and 7.3 rebounds per game. It was also his only post-military season in which the Celtics did not win the NBA championship; the Bob Pettit-led St. Louis Hawks (who also featured Cliff Hagan, Ramsey's ex-college teammate) defeated them in the NBA Finals. Ramsey was also a head coach for one season (1970–71) in the ABA with the Kentucky Colonels, who were led by two former Kentucky Wildcats – Issel, a rookie, and Louie Dampier. Ramsey was named coach 17 games into an 84-game season (which began with Gene Rhodes coaching the first 15 games and fellow Kentucky alum Alex Groza coaching the next two) and, though he had a 32-35 record, coached the Colonels into the playoffs. The Colonels lost to the Utah Stars (who were coached by Sharman, Ramsey's ex-Celtic teammate) in the 1971 ABA Finals, 4 games to 3. Joe Mullaney replaced Ramsey as coach the following season. Prior to coaching in the ABA, Ramsey had been Red Auerbach's first choice to replace his mentor as Celtics coach after Auerbach retired at the end of the 1965–66 season. However, Ramsey decided to move back to Madisonville; his father, Frank Sr., wasn't in good health and Frank Jr. had three children to raise. Auerbach is often credited throughout basketball with creating the sixth man. Though Ramsey was one of the Celtics' best players, he felt more comfortable coming off the bench and Auerbach wanted him fresh and in the lineup at the end of close games. Ramsey was the first in a series of sixth men who won championship rings with the Celtics.