49ers' Chris Borland becomes latest young NFL star to retire early

The San Francisco 49ers have lost another inside linebacker to retirement.

One week after losing All-Pro backer Patrick Willis to an early retirement, Chris Borland is calling it a career after a standout rookie season. It's unprecedented for a star player like Borland to retire after just one season, but the same could be said of how rare it is for a player as young as the 30-year-old Willis who called it quits during his prime.

Here's the report on Borland from ESPN's Outside the Lines:

Chris Borland, one of the NFL's top rookies last season, told "Outside the Lines" on Monday that he is retiring because of concerns about the long-term effects of repetitive head trauma.

Borland, 24, said he notified the 49ers on Friday. He said he made his decision after consulting with family members, concussion researchers, friends and current and former teammates, and studying what is known about the relationship between football and neurodegenerative disease.

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

Borland, a fourth-round pick out of Wisconsin, had 107 tackles and a sack in 14 games as a rookie. He finished fourth out of 60 qualified inside linebackers in Pro Football Focus' grading system.

It's becoming almost normal, at least this offseason, for NFL players with the ability to impact a team, to call it quits due to health concerns and/or the pursuit of other opportunities.

Jason Worilds, Jake Locker, Willis and now Borland have all retired this offseason, despite likely being able to either contribute at a high level, or sign a contract with a team paying them millions of dollars. It's sad Borland won't be able to earn that, as he was on pace to be one of the best linebackers in football.