NFL coaches and executives have become concerned by the lack of experience of the players they're putting on the field.

Due to changes at both ends of the age spectrum, players have become younger. Record numbers of less experienced rookies are entering the league which is pushing out veterans.

“Everything from defensive linemen not knowing where their eyes should be looking, not knowing where blocks are coming from,” said John Harbaugh. “Defensive backs not recognizing routes, not knowing how to burst, stop, start, and change direction so they don’t tear their ACLs. Offensive linemen not knowing where blitzers are coming from. Just not a lot of technique anywhere.”

In 2015, the league-wide average age hit its lowest mark since Football Outsiders started keeping track a decade ago. In 2006, the average age of the players on the field was 27.2; in 2015, it was 26.6. On offenses alone, the average age of players on the field dipped almost a full year, from 27.6 in 2006 to 26.8 last year.

“This is a real serious concern,” Harbaugh said. “Not just for the quality of the game, but for the well-being of these young guys coming into the NFL.”

Despite medical and nutritional advancements, NFL careers are ending earlier for anyone who isn’t a quarterback or a special teams cog.

The 2016 NFL Draft featured 107 early entrants, which was easily a record.

“Let’s be honest, the younger the league, the less experienced the league is and with that, the quality of play doesn’t start off at the same level,” said Mike McCarthy. “I think what you see, particularly in the early part of the season, is a reflection of that.”

“The way the CBA is structured now, it’s really no different from any other workforce in that you want to find the healthiest, youngest, least-expensive talent and infuse it into your corporation,” said Titans general manager Jon Robinson. “We’re the same model.”