Is the beginning of the end for the NFL?

Indianapolis Colts quarterback Andrew Luck’s sudden retirement at age 29 took most fans by surprise.

But for some observers, it was just the latest sign the National Football League as we know it may no longer exist in just a few decades.

“I haven’t been able to live the life I want to live. It’s taken the joy out of this game. The only way forward for me is to remove myself from football. This is not an easy decision. It’s the hardest decision of my life. But it is the right decision for me,” said Luck, who at just 29 years old has already suffered a lacerated kidney, a torn abdomen, torn ribs, at least one concussion and nagging ankle injuries.

And he’s hardly the only high-profile player to suddenly quit. The New England Patriots’ Pro Bowl tight end Rob Gronkowski retired at age 30 after suffering a leg injury in the Super Bowl that resulted in a full liter of blood being drained from bruised muscles. In nine seasons he also suffered multiple torn knee ligaments, concussions, a broken back, and herniated discs.

San Francisco 49ers linebacker Chris Borland retired at age 23, citing the long-term effects of concussions and Seattle Seahawks linebacker Joshua Perry retired at 24 after his sixth concussion.

Injuries in football are hardly new, but they’re happening in an era in which players not only know more about the long-term health effects, but the players dealing out the punishment are faster, stronger and bigger than before.

A full-speed midfield collision between two players grows much more damaging and violent when each player is about 20 pounds heavier than they were 10 years earlier.

That leaves the future of the league itself in doubt. Youth football leagues report reduced participation due to parents’ concerns about concussions.

With more and more players retiring in their 20s, can the NFL survive as a league when fewer kids are playing and top stars sign that first contract and then quickly get out?

The NFL could become like Major League Baseball, which still exists but isn’t drawing nearly the revenue, TV ratings and attendance they did decades earlier as youth participation declines and top stars opt for other sports.