San Francisco 49ers linebacker Chris Borland is retiring from football due to worries about head trauma.

Borland, 24, told ESPN’s “Outside the Lines” on Monday that he informed the 49ers of his decision Friday. He was the team’s leading tackler last season as a rookie. Borland saw some of his action filling in for injured veteran Patrick Willis. Last week, Willis retired at 29, citing foot injuries.

Even though he told ESPN he was diagnosed with only two concussions, both while in high school, one while playing soccer and the other while playing football, Borland said he will not change his mind about retiring.

“I just honestly want to do what’s best for my health,” said Borland, who is 5-foot-11, 248 pounds. “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 till 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.”

According to “Outside the Lines,” post-mortem studies found more than 70 former NFL players had progressive neurological disease.

“I’ve thought about what I could accomplish in football, but for me personally, 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,” Borland said.

A third-round draft pick in 2014 out of Wisconsin, Borland recorded 107 tackles, one sack, two interceptions, one fumble recovery and five passes defensed during his lone season with the 49ers.

In addition to Borland and Willis, Pittsburgh Steelers linebacker Jason Worilds, 27, and Tennessee Titans quarterback Jake Locker, 26, also retired recently. Neither Worilds nor Locker cited health concerns when making their announcements.