Earl Morrall: 21 seasons
With all apologies to Nick Foles, Earl Morrall is probably the greatest backup quarterback of all time. With the Colts, Morrall replaced an injured Johnny Unitas in both the Super Bowl III and Super Bowl V seasons, winning the title in the latter. He then moved to the Dolphins, where he replaced an injured Bob Griese during the 1972 season, winning 11 of Miami’s 17 games that season. (Griese did start the Super Bowl, though.) He later became quarterbacks coach at the University of Miami, where he worked with Jim Kelly, Bernie Kosar and fellow 20-season club member Vinny Testaverde.