Brady needed the ecosystem around him to function at a high level, and it did so for a long period. In interviews with industry sources throughout the NFL, the similarities noted between Brady's Patriots and Mahomes' Chiefs are many. Those sources also noted that the league is different than it was in 2006, and highlighted the many ways the ecosystem that can produce an ultrarare, multidecade NFL dynasty is fragile. Kansas City does not have the league's deepest resources and has a reputation for being cautious in how it utilizes them. Andy Reid, its 66-year-old head coach and organizational architect, has an uncertain retirement timetable.

But all agree the Chiefs are set up for greatness, perhaps on an unprecedented scale. Mahomes and Brady know it, too.