NFL Connections #115, Answers
The full solution: all four groups and the 16 names, sorted from the easiest group to the trickiest.
Never left their first team
Dan Marino, Bruce Matthews, Jack Lambert, Dan Fouts
Traded in their prime
Herschel Walker, Khalil Mack, Tyreek Hill, Davante Adams
Blockbuster free-agent signings
Reggie White, Drew Brees, Peyton Manning, Kirk Cousins
Legends in a strange last uniform
Johnny Unitas, Joe Namath, Jerry Rice, Emmitt Smith