(Rick Osentoski, / AP)

Updated at 11:10 a.m. with NFL statement

The news Monday night was shocking, even at a time in which the NFL has had one shocking headline after another. Chris Borland is quitting one of the most coveted jobs in America, retiring as a linebacker for the San Francisco 49ers at 24 because he’s concerned about the long-term effects of repetitive head trauma. Now, just weeks before a new crop of college kids are drafted into the league, the NFL finds its offseason dominated by stories about young players who are quitting.

Borland becomes the fourth player at the age of 30 or younger to retire in just the last week, joining Patrick Willis, another 49ers linebacker who quit six days earlier because of pain in his feet. Pittsburgh Steelers linebacker Jason Worilds is quitting at 27 to do religious work and Jake Locker, a Tennessee Titans quarterback who was an NFL bust, says he “has no burning desire to play.”

Last year, Seattle Seahawks wide receiver Sidney Rice retired because of his increased awareness of the dangers of concussions, an awareness that was heightened after watching a documentary in which Dallas Cowboys Hall of Famer Tony Doresett spoke of his daily battles with deteriorating health brought on by chronic traumatic encephalopathy. In early March, Rice and New York Giants punter Steve Weatherford, announced that they would donate their brains to science research when they die. Rice estimated that he has had eight concussions; Weatherford two. But, as everyone is becoming increasingly aware, small, repetitive hits take their toll, too.

[Borland makes surprise announcement |Will early retirements become more prevalent? ]

That’s why playing the game just wasn’t worth it for Borland. A third-round draft pick out of Wisconsin, he was one of the top rookies in the NFL last season and was due to make $530,000 in 2015. A history major, Borland made his choice after speaking with concussion experts and former players and will undergo baseline tests to monitor his health and “contribute to the greater research.”

“I just honestly want to do what’s best for my health,” Borland told ESPN’s Mark Fainaru-Wada and Steve Fainaru. “From what I’ve researched and what I’ve experienced, I don’t think it’s worth the risk … I feel largely the same, as sharp as I’ve ever been, for me it’s wanting to be proactive. I’m concerned that if you wait ’til you have symptoms, it’s too late. … There are a lot of unknowns. I can’t claim that ‘X’ will happen. I just want to live a long healthy life, and I don’t want to have any neurological diseases or die younger than I would otherwise.”

Over the last few years, suicides by former players have been gaining increasing attention, with Junior Seau’s in May 2012 the tipping point on a crisis the NFL has been slow — putting it charitably — to address. The league has committed funds to the study of concussion prevention and teaching how to play the game smartly, but, for every positive step forward, there’s a regression as another prominent citizen (President Obama) or former player (Mike Ditka) expresses reservations about letting children play the sport. Days after Seau’s May 2012 suicide, Jacob Bell walked away from the Cincinnati Bengals at 31, an outlier at the time.

This video from the CDC illustrates and explains the science behind a concussion and the importance of recovery time for the human brain. (CDC via YouTube)

“I’ve been thinking about some different things, thinking about health, thinking about the future of my family having to deal with some kind of crazy disease that nobody even knows about, where people want their brains studied after they’re dead, donating their brains to research,” Bell said then. “It’s just crazy to see how someone like Junior Seau took his own life over — God knows what he was really struggling and dealing with. But you have to believe it came from the game of football. I want to get out before the game makes me get out, where I can get out on my own terms, and I can limit the amount of stress and negative impact that the game would leave on me. I played under a guy, Mike Munchak in Tennessee, and I used to watch him as he was running around the practice field for a half hour before practice, and I’d see the way he’d run. He played 13 seasons, he played all 13 seasons with no cartilage in his knees. And I thought to myself, I don’t want to look like that. I don’t want to be at the point where I’m jeopardizing my true health for money pretty much. For money and for celebrity.”

Borland had the same realization. “I just thought to myself, ‘What am I doing? Is this how I’m going to live my adult life, banging my head, especially with what I’ve learned and knew about the dangers?'” Borland told Fainaru and Fainaru-Wada. “… I’ve thought about what I could accomplish in football, but when you read about Mike Webster and Dave Duerson and Ray Easterling, you read all these stories and to be the type of player I want to be in football, I think I’d have to take on some risks that as a person I don’t want to take on.”

San Francisco 49ers linebacker Chris Borland, a leading rookie last season, is retiring from the NFL over health concerns related to repeated head trauma. (Reuters)

All three of those former players were found to be suffering from CTE after their deaths. CTE led to memory loss, aggression, confusion, depression and suicidal thoughts, even as the men became increasingly aware that something was terribly wrong. Duerson, like Seau, chose to shoot himself to death in the chest to preserve his brain for study. Seau was recently voted into the Pro Football Hall of Fame and his induction ceremony this summer is sure to be filled with praise for his courage and cautionary reminders about the dangers of the game. It will be perhaps the most crystallizing moment yet for the issue and the future of the game. The NFL was sufficiently aware of that to issue a statement Tuesday morning (via Pro Football Talk)  in which Jeff Miller, its senior vice president for health and safety policy, pointed out that the game “has never been safer.”

“We respect Chris Borland’s decision and wish him all the best. Playing any sport is a personal decision.

“By any measure, football has never been safer and we continue to make progress with rule changes, safer tackling techniques at all levels of football, and better equipment, protocols and medical care for players. Concussions in NFL games were down 25 percent last year, continuing a three-year downward trend. We continue to make significant investments in independent research to advance the science and understanding of these issues. We are seeing a growing culture of safety. Everyone involved in the game knows that there is more work to do and player safety will continue to be our top priority.”

For now, sky-high TV ratings and the obscene revenues they generate continue and for every player that quits, a 100 more will take their place — until children whose parents won’t let them play grow up and the pool of players shrinks precipitously. The real effects on the game might not be felt for a few more years, but they’re going to be devastating. “Obviously, guys will continue to play football,” ESPN’s Kirk Herbstreit tweeted, “but I guarantee the Borland early retirement gets the attentionof a lot of moms and youth football.”

It’s another watershed moment for the game.