Chris Borland, the San Francisco 49ers linebacker who was one of the top rookies this season, is retiring at 24 due to concerns over long-term head trauma, ESPN reports.

"I just honestly want to do what's best for my health," Borland told ESPN's Outside the Lines. "From what I've researched and what I've experienced, I don't think it's worth the risk."

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Borland, a University of Wisconsin graduate, was the NFL's 77th draft pick last year. He signed a four-year contract with the 49ers worth nearly $3 million, including a $617,436 signing bonus. He told his team of his decision on Friday.

"While unexpected, we certainly respect Chris' decision," the team's general manager, Trent Baalke, said. "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."

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Borland says he's suffered two concussions so far, one during a soccer game in eighth grade and another while playing football in high school.

"I feel largely the same, as sharp as I've ever been. For me, it's wanting to be proactive," Borland said. "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."

Brain injury and long-term effects of football have been a hot topic lately, with a 2014 study revealing that 76 of 79 deceased former players had evidence of a degenerative brain disease.

"I just thought to myself, 'What am I doing?'" Borland said. "Is this how I'm going to live my adult life, banging my head, especially with what I've learned and know about the dangers?"

What do you think of Borland's decision?

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