If Junior Seau isn’t the National Football League’s worst nightmare, Chris Borland should be.

Seau shot and killed himself in 2012 at age 43 — just three years removed from a 20-year Hall of Fame NFL career. Tissue samples showed that Seau, a linebacker, had chronic traumatic encephalopathy, or CTE, a degenerative brain disease linked to repeated head hits and brain trauma.

Borland, who also played linebacker, shocked the league Monday when he announced his retirement after just one promising season with the San Francisco 49ers. Borland said fear about the possible long-term effects of head injuries — not recent injuries or symptoms — prompted his decision.

“From what I’ve researched and what I’ve experienced, I don’t think it’s worth the risk,” Borland, 24, told ESPN. “ … 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.”

What makes Borland’s decision so unusual is that the former University of Wisconsin star had not been diagnosed with a concussion since his sophomore year of high school football. He also suffered one while playing eighth-grade soccer. He told ESPN that he thought he might have sustained a concussion during training camp with the 49ers but that he kept playing because he was trying to make the team.

Borland said he talked with concussion experts as well as current and former teammates before giving up the game and the millions of dollars that could have come his way. He earned a bachelor’s degree in history at Wisconsin and told ESPN he might pursue a career in sports management.

Citing rule and equipment changes, the NFL’s senior vice president for health and safety, Jeff Miller, said in a statement that “football has never been safer.”

However, Miller added, “Everyone in the game knows that there is more work to do, and player safety will continue to be our top priority.”

We hope that’s the case, and that Borland’s decision will intensify the focus on making football a safer sport from youth leagues to the NFL.