I talked to three current coaches in the NFL, one of whom is a former head coach, and all three singled out a player's ability to teach as an essential indicator of potential future head-coaching success. For this reason, players who aren't as naturally gifted -- who require the teaching of others to succeed on the field -- are often more promising coaching prospects than great players, who often don't really need help from anyone to thrive. As someone who watched Tom Landry -- who played for the Giants -- rack up wins and trophies while prioritizing teaching as coach of the Cowboys, I can personally testify to the importance of tutelage. There's another reason you don't see a lot of elite players become head coaches these days: They tend to earn so much money during their playing careers that they aren't necessarily motivated to work long, hard hours after hanging up the cleats.