Perhaps the least quantifiable measure of a great team is the locker room’s ability to develop itself. That takes shape in many ways, but particularly with respect to veteran players introducing younger players to the league, to the team, to the system, to the position, or whatever the case may be.
The Pittsburgh Steelers relied on this system for many years, and those younger players would often take the place of the older veterans when free agency hit. These days they’re more likely to retain the older veteran—they’ve become harder to replace in many respects, particularly at some positions—but the culture of development remains.