Chris Borland's decision to retire due to health concerns after one successful rookie season triggered shockwaves around the NFL.
"I just honestly want to do what's best for my health," Borland told ESPN. "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."
One NFL executive told The Baltimore Sun it was odd to see Borland retire at 24 years old without a significant known history of head injuries. However, the executive predicted that Borland's decision wouldn't create a trend among NFL players.
In meeting Borland last year, first at the Senior Bowl and then at the NFL scouting combine -- where he met with the Ravens -- I was struck by how passionate he was about football.
Although relatively undersized at 5-foot-11, 245 pounds, Borland's toughness and instincts allowed him to excel. He was often compared to other shorter linebackers like Zach Thomas, London Fletcher and Chris Spielman, whom he emulated.
Borland told me he was the most complete linebacker in the draft, and the 49ers picked the three-time All-Big Ten Conference selection in the third round.
"I'm confident that I am, and I don't know that there are a lot of players that are a better all-around athlete,"said Borland, who went on to have 107 tackles and a sack as a rookie. "I don't get maybe a lot of credit for it. I'm small, and straight-line speed is not my strong suit necessarily.
"I feel like I'm the toughest guy here, or at least one of them. We've got a lot of tough guys here at the combine, but I've played through things, no complaint, practice hard, all the right things."
It remains to be seen whether other young players will follow suit.
Former Pittsburgh Steelers linebacker Jason Worilds retired to devote more time to his religion, according to sources. And former Tennessee Titans quarterback Jake Locker retired after struggling as a former first-round draft pick, saying in a statement that he no longer had the desire to play.
NFL senior vice president of health and safety policy Jeff Miller issued a statement about Borland's decision:
"We respect Chris Borland's decision and wish him all the best," Miller said. "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."