Another prominent NFL player is walking away from the game in his prime.
"I just honestly want to do what's best for my health," said Borland, who met with prominent concussion researchers before making his decision. "From what I've researched and what I've experienced, I don't think it's worth the risk."
Borland, 24, said he has been diagnosed with two concussions in his life -- once while playing soccer in eighth grade and again while playing football during sophomore year of high school. He said he believed he might have suffered a third concussion during training camp, but played through it because of his concern about making the team as a third-round pick out of Wisconsin.
"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?'"
Jeff Miller, the NFL's senior vice president of health and safety policy, released the following statement Tuesday morning.
"We respect Chris Borland's decision and wish him all the best. Playing any sport is a personal decision," the statement read.
"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."
The 49ers did not see Borland's retirement coming, but wished him well in a statement from general manager Trent Baalke.
"While unexpected, we certainly respect Chris' decision," said Baalke on Monday night. "From speaking with Chris, it was evident that he had put a great deal of thought into this decision. He was a consummate professional from day one and a very well respected member of our team and community. Chris is a determined young man that overcame long odds in his journey to the NFL and we are confident he will use the same approach to become very successful in his future endeavors. We will always consider him a 49er and wish him all the best."
Borland made the final roster and became one of San Francisco's best defensive players after Willis went to injured reserve after six games. Borland said his success -- which included an NFC Defensive Player of the Week award and a vote for Defensive Rookie of the Year -- didn't make his decision any more difficult.
Borland joins quarterback Jake Locker and linebacker Jason Worilds as the third NFL player to step away from the game voluntarily before age 30 this season. Locker, 26, said "he no longer (had) the burning desire necessary to play the game for a living." Worilds, 27, retired reportedly to devote time to his religion, the Jehovah's Witnesses.
Borland's decision is sure to reverberate through the NFL. For the Niners, a trying offseason takes another unexpected turn. The departure of Willis and now Borland turns linebacker from a position of strength into one of weakness.