CSN Bay Area

One week after Patrick Willis’ sudden retirement, 49ers linebacker Chris Borland has informed the team he is also ending his football career due to the long-term effects of repetitive head injuries.

Borland, 24, who made the NFL All-Rookie team, after leading the 49ers in tackles while making just eight starts in place of Willis, told ESPN's "Outside the Lines" on Monday that he notified the 49ers of his decision on Friday.

The 49ers were not immediately available for comment on Monday night.

[RELATED: Baalke: Borland 'put a great deal of thought into this decision']

Borland said he made his decision after speaking with family members, concussion researchers, friends and current and former teammates, according to the report from Mark Fainaru-Wada and Steve Fainaru, which was posted on ESPN.com. Borland said he also studied what is known about the relationship between football and neurodegenerative disease.

Borland was a third-round draft pick from Wisconsin. He signed a four-year, $2.927 million contract, including a $617,436 signing bonus. He will likely be forced to return a large portion of his signing bonus because of his decision to retire.

"I just honestly want to do what's best for my health," Borland explained. "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."

Borland (5 foot 11, 248 pounds) was an All-American linebacker and Big-Ten Defensive Player of the Year. Some teams believed his history of shoulder injuries would preclude him from a long NFL career.

Borland said he began to have second thoughts about a football career in training camp. He told OTL that he sustained what he believed to be a concussion in training camp but did not alert the 49ers' medical staff because of his desire to make the team.

"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?'” Borland said.

Borland said he does not have a lengthy history of diagnosed concussions. He said he sustained one concussion while playing soccer in eighth grade, and another in his sophomore year of college playing football.

With the sudden retirements of Willis and Borland, the 49ers are left shorthanded at inside linebacker. NaVorro Bowman is expected to return this season after missing last season while rehabbing a knee injury sustained in the NFC Championship game in January 2014. Michael Wilhoite started all 16 games last season in place of Bowman.

Willis, 30, announced his retirement last week, citing the physical toll the game has taken on his feet.