San Francisco: Chris Borland, a 24-year-old linebacker for the San Francisco 49ers, told ESPN on Monday he is retiring from the National Football League over health concerns due to repeated head injuries.

“I just honestly want to do what’s best for my health,” Borland told ESPN. “From what I have researched and what I’ve experienced, I don’t think it’s worth the risk.”

He becomes the most prominent NFL player to turn his back on a rich contract, a four-year deal worth just under $3 million (Dh11 million) in Borland’s case, over concerns about brain injuries.

Such a condemnation of the dangers and safety worries in the world’s richest sports league comes after seasons of concern for NFL players over the long-term impact of repeated blows to the head, including studies linking the NFL to neurodegenerative diseases.

In his rookie NFL season last year, Borland made 108 tackles, a quarterback sack and two interceptions over 14 games before an ankle injury in December ended his season.

But the third-round NFL Draft choice told ESPN that he notified the 49ers last Friday of his decision to leave the sport, saying he was being “proactive” despite feeling “as sharp as I’ve ever been.”

“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 49ers lost linebacker Patrick Willis last week. He announced his retirement at age 30 after playing only six games last season due to a toe injury. Borland said the decision by Willis played no role in his decision, which includes plans to return to college and study sports management.