[1][2] When inducted into the Blair County Sports Hall of Fame in 1987, Flanagan noted that he had not been a star player in high school and was not a starter until his senior year.
[3] As a senior, he was the starting center for the 1964 Boilermakers team that featured Bob Griese at quarterback and compiled a 6–3 record and finished in third place in the Big Ten Conference.
Flanagan was selected by the conference coaches for the United Press International as the second-team center on the 1964 All-Big Ten team.
[3] While playing for the Lions, Flanagan supplemented his income in the off-season selling steel to the automobile companies, selling real estate, and working for a beer distributorship owned by former Detroit Tigers star Vic Wertz.
[3] Flanagan took over as the Lions' starting center as a rookie in 1965 and held the position for the next ten years.
[1] He was also selected as a second-team All-NFL player by the Newspaper Enterprise Association in 1969 and Pro Football Writers of America in 1970.
[9] However, he was released on waivers by the Rams in early September 1977 prior to the start of the regular season.
[10] In 1984, Flanagan was hired as the offensive line coach for the Oakland Invaders of the United States Football League.