Twenty-four-year-old San Francisco 49ers linebacker Chris Borland says he's retiring over concerns about his health.
Borland told ESPN's "Outside the Lines" he was worried about the long-term effects of repetitive head trauma, an issue that's been raised in recent years as studies have linked the sport with neurodegenerative diseases.
"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."
Borland had 108 tackles, one sack and two interceptions in 14 games as a rookie last season before being placed on season-ending injured reserve in December with an ankle injury.
The third-round draft pick notified the 49ers on Friday that he would retire, according to ESPN.
Borland told ESPN he feels "as sharp as I've ever been" but wanted to be "proactive" in avoiding any potential effects from playing in the league.
"I'm concerned that if you wait till you have symptoms, it's too late," Borland said. "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."
The news came six days after 49ers linebacker Patrick Willis announced his retirement at the age of 30 after missing all but six games last season because of a toe injury.
Borland said Willis' retirement had no effect on his decision, according to ESPN. The 5-foot-11, 250-pound linebacker told ESPN there was no chance he would change his mind.