Selected in the fifth round out of Purdue in 1965, Ed Flanagan had an elite athletic foundation and technical mastery that allowed him to make an immediate impact. Stepping onto the field as a rookie, he instantly claimed the starting center spot, anchoring the middle of Detroit's offensive line with quiet brilliance for the next decade.

Flanagan stood out for his exceptional leverage, swift lateral movement, and flawless line calls, serving as the unsung engine for Detroit's offense. Operating in the trenches during a punishing era of interior line play, he earned immense respect from opposing defensive tackles across the NFC who recognized his tactical consistency. His exceptional play earned him four Pro Bowl selections (1969, 1970, 1971, 1973) and two Second-Team AP All-Pro nods (1969, 1970), solidifying his reputation as one of the premier centers of his era.

From 1965 through 1974, he anchored the pivot through a grueling 129 consecutive games, serving as a steady protector for quarterbacks like Greg Landry and Bill Munson while clearing lanes for power runners like Altie Taylor. After ten seasons in Detroit, he capped off his career with a two-year stint with the San Diego Chargers before retiring. 

His contributions to the franchise were later recognized with selections to both the Lions 75th Anniversary Team and the All-Time Team.