'A Football Life': Calvin Johnson explains why he retired after the 2015 NFL season

'A Football Life': Members from the unbeaten 1972 Miami Dolphins squad talk about how Pro Football Hall of Fame head coach Don Shula's decision to put recovered Miami Dolphins quarterback Bob Griese back into the lineup as the team's starting quarterback during the AFC Championship game against the Pittsburgh Steelers acted as a necessary catalyst that helped send the team back to a second consecutive Super Bowl.

The 1972 Miami Dolphins talk about how their team's defense comprised of mostly anonymous and selfless players embraced the 'No Name Defense' nickname bestowed upon them with a badge of honor on their way to stout defensive play.

Miami Dolphins players talk about how their 'unselfish' backfield trio powered their unbeaten record in 1972 NFL season on the 'A Football Life' episode about their perfect season.

The Miami Dolphins' season-opening road win against the Kansas City Chiefs sets the tone for their perfect 1972 NFL season.

The Miami Dolphins complete their perfect 1972 NFL season with a Super Bowl VII win over the Washington Redskins at the Los Angeles Memorial Coliseum.

Miami Dolphins legends recount Pro Football Hall of Famer Don Shula's unrivaled work ethic as the Dolphins' head coach in their perfect 1972 NFL season.

Legendary Pittsburgh Steelers running back Franco Harris gets enshrined as a member of the Pro Football Hall of Fame's Class of 1990.

Pro Football Hall of Fame running back Franco Harris sticks up for Pittsburgh Steelers quarterback Terry Bradshaw in the Steelers' Super Bowl XIII win over the Dallas Cowboys.

'A Football Life': Pro Football Hall of Fame running back Franco Harris and his Pittsburgh Steelers teammates talk about his signature running style and how Franco's reputation for running out of bounds to avoid contact would disappear in short yardage situations when he needed to get the yards.

'A Football Life': Pittsburgh Steelers Pro Football Hall of Fame running back Franco Harris talks 'The Immaculate Reception' with Oakland Raiders linebacker Phil Villapiano.

Pittsburgh Steelers Hall of Fame running back Franco Harris talks about winning offensive rookie of the year after being drafted by the Pittsburgh Steelers in 1972.

Pittsburgh Steelers Pro Football Hall of Fame running back Franco Harris talks about his 'Franco's Italian Army' fan club and how Frank Sinatra made his way into it.

Pittsburgh Steelers Hall of Fame running back Franco Harris emerges as a New Jersey high school football star before establishing a solid collegiate career with the Penn State Nittany Lions.

'A Football Life': Pittsburgh Steelers Hall of Fame quarterback Terry Bradshaw relives Steelers Hall of Fame running back Franco Harris' heads-up play on 'The Immaculate Reception' against the Las Vegas Raiders on December 23, 1972.

Former New England Patriots wide receiver Julian Edelman talks about his retirement decision and his post-playing broadcasting career.

Former New England Patriots wide receiver Julian Edelman talks about overcoming the adversity sustained from his injury and suspension by winning MVP in Super Bowl LIII.

Former New England Patriots wide receiver Julian Edelman etches his name in history with two iconic Super Bowl performances.

Former New England Patriots wide receiver Julian Edelman talks about connecting with his faith and Jewish ancestry.

Former New England Patriots wide receiver Julian Edelman talks playing with Tom Brady and how the legendary quarterback helped Edelman evolve into a top wide receiver

Former New England Patriots wide receiver Julian Edelman talks about how he earned roster spot on the Patriots as a late-round draft pick making a position change from quarterback to wide recevier.

Former New England Patriots wide receiver Julian Edelman talks about how he blossomed as a collegiate quarterback at San Mateo College before ultimately transferring to Kent State.

Former New England Patriots wide receiver Julian Edelman talks about what it was like being a kid playing Pop Warner footbal and being coached by his father.

Pro Football Hall of Fame running back Edgerrin James recounts how his early passion for football turned him into a high school football star.

Former Indianapolis Colts and Arizona Cardinals running back Edgerrin James puts his unique stamp on his Pro Football Hall of Fame speech.

Pro Football Hall of Fame running back Edgerrin James tells the story about how his time with the Arizona Cardinals included flying back and forth to Tampa Bay, Florida to visit the mother of his children while she was sick.