ATLANTA — Following his second day of work as an intern in the mental health program at the Carter Center last month, Chris Borland was driving home past a high school. On a field situated along the road, he saw a football team in the middle of a spring practice. Borland pulled over and watched for 10 minutes, not out of nostalgia for a game he left behind, but rather fixating on the players as their helmets collided repeatedly during a series of contact drills.

“It’s just unnecessary,” Borland said. “I think you can teach technique and scheme and everything without hitting your helmets together.”

As Borland watched that May practice, he found himself at the intersection of his former and current life. He began his 10-week unpaid internship at the nonprofit public policy center founded by Jimmy and Rosalynn Carter about 14 months after he stunned the football-watching world with his abrupt retirement from the NFL. The decision came following a successful rookie season as a linebacker with the San Francisco 49ers and stemmed from wariness over the prospective consequences of brain injuries, particularly chronic traumatic encephalopathy or CTE.

[Chris Borland on the NFL’s future and his past year]

All of that swirled in Borland’s mind as he watched those high school spring drills.

Borland celebrates after a fumble by New Orleans Saints quarterback Drew Brees during the 2014 season. (Usa Today Sports / Reuters/Usa Today Sports)

“I thought of a lot of different things,” Borland said last week, sitting in a Carter Center conference room. “The decision I made — when I see kids’ heads bang together, I think of [how] your brain sits unfastened in a pool of cerebrospinal fluid. And it’s gelatinous and it’s crashing against a hard skull. So that’s kind of an image I always have when football’s on.”

‘I know it’s a sound decision’

Borland has been busy, he says, since his March 2015 retirement announcement. He spent time in Europe. He has done work with a list of organizations that includes One Mind, a nonprofit dedicated to benefiting those affected by brain disease, and Gridiron Greats, which provides assistance to former NFL players in need.

When he moved out of San Francisco last year and drove to his parents’ house in Dayton, Ohio, he listened to an audio version of Jimmy Carter’s “Beyond the White House: Waging Peace, Fighting Disease, Building Hope.” He was particularly interested in Rosalynn Carter’s work on mental health issues. Borland ended up visiting the Carter Center last year and applying for this year’s internship program.

The center’s work does not involve traumatic brain injuries. But Borland said he finds the center’s global efforts to destigmatize mental illness relevant to the experiences of many former NFL players.

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Borland returned most of the signing bonus paid to him by the 49ers. (Al Bello)

Borland participated in a mental health forum his first week at the center. He was busy last week helping to reduce a list of journalism fellowship applicants. He enters contacts into a database. He’s happy to get the sort of office-work experience, he said, that he missed while going straight from being a college student-athlete to an NFL player.

“He came in and was very straightforward in his presentation of himself, not in any way aggrandizing,” said Thomas H. Bornemann, the director of the mental health program at the Carter Center. “He comes in on time or early each day, plugs in and goes to work. And he works until after closing hours.”

Borland said he will never play football again, and he doesn’t see himself getting into coaching, unless it’s coaching a youth flag football team. He does envision himself remaining tied to the sport, however, through his work on matters related to football and brain injuries.

“I think I’m connected to this issue in some capacity, football and brain damage,” Borland said. “So carving out a way to address it tactfully is important to me no matter what I go on to do. I’ve got a wide variety of interests. But I think I’ll be connected to this for a long time. But I hope to be, too, because I think there’s a lot of misinformation. I’d like to be a voice of reason.”

Borland said he does miss football, particularly the camaraderie found with teammates. But he does not second-guess his retirement choice.

“Intellectually, I know it’s a sound decision,” Borland said. “So I don’t regret that. More information has come out since I walked away that kind of reaffirmed my decision.”

He did not watch a single NFL game last season, he said, other than glancing at the screen if a game happened to be on a television while he was in a restaurant or bar. That level of detachment was made a bit easier by spending the first half of the season in Europe. He is in touch with some former 49ers teammates “nearly daily,” he said.

“It’s surprisingly cordial,” Borland said. “This is a lot of times construed as an adversarial arena, pro- or anti-football. But the analogy I use is I have friends who smoke cigarettes. I don’t tell them statistics about cigarette smoking. I don’t tell my friends who play football statistics about brain damage. It’s just two good friends with a healthy disagreement.”

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Upon his unusually early retirement, some viewed him as a trendsetter, one who could set an example for other players to walk away from the game, prioritizing long-term health over an NFL career. ESPN even went so far as to label him “the most dangerous man in football.” Borland said he has heard from six to 10 NFL players seeking information about football and brain disease, but he says he is not advocating for them to follow in his footsteps.

“I don’t think they were necessarily at a point where they were asking me to help them make their final decision,” Borland said. “But [it was] more of, ‘Hey, where did you go? What have you learned?’ Things like that.”

Of that group, two players were nearing a final decision about possible retirement, according to Borland, who did not identify the players. He said he did not offer them a recommendation, noting he was not a neurology expert and that advising players to follow a particular course would be “inappropriate.”

Chris Nowinski, the executive director of the Concussion Legacy Foundation, says he has fielded multiple requests from NFL players who want to speak with Borland.

“One year later, Chris Borland’s decision to retire still resonates within the football community,” Nowinski said via email. “I have been asked by a number of current NFL players for an introduction to Chris, and I hope he continues to share his experience and knowledge with the world. In addition, his continued efforts to educate youth coaches and parents on concussions and CTE, as well as the appropriate age to begin tackle football, is a tremendous service.”

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In Borland, any current NFL player contemplating early retirement now has a resource Borland didn’t have. Borland had to figure out for himself how to find the information that shaped his retirement deliberations. He started with Internet searches, then reached out to experts. In all cases, he scrutinized his findings.

“I wanted to avoid making any decision based off anecdotes,” he said. “As much empirical data as I could gather was really important to me. I was the biggest critic. I spent all of the fall saying, ‘Okay, the Boston University brain bank — well, that’s a biased sample. Okay, the NFL actuary report that there are guys who have brain damage — well, that’s a third of guys. Maybe I’ll be in the 70 percent.’ . . . And then it got to a point where it was just hard for me to deny . . . especially with having goals of playing for a decade.”

There was also his role on the field and his previous medical history to consider.

Borland said he’s had two diagnosed concussions and played through another in training camp his rookie season in the NFL. He subsequently underwent a clinical evaluation with UCLA researcher Christopher Giza that found, according to Borland, he likely had suffered a dozen concussions of similar severity over his lifetime, about eight of them related to football.

“If I were in it for the money or to play a few years, maybe you can say, ‘Well, I’ll be the outlier. I’ll be fine,’ ” Borland said. “But inside linebacker with concussion history with the goals of playing for a decade — I felt that I’d fit into the category of guys who had impairment.”

‘[It] happens extremely fast’

Borland, 25, walked away from football following a rookie season with the 49ers in which he was credited with 107 tackles, one sack and two interceptions in 14 games . The third-round draft pick from Wisconsin had three seasons remaining on a four-year contract worth a little more than $2.9 million. That contract was not guaranteed for the seasons Borland did not play, and he said later he was returning three-fourths of his $617,436 signing bonus to the 49ers. He made an estimated $574,000 from the 49ers, including his salary and a prorated portion of his signing bonus, for his rookie season.

He doesn’t fret about the money he left behind, but he said he also understands some players do not have the financial leeway to do what he did. That aspect is something that could reshape the demographics of the NFL, Borland believes.

“Dementia pugilistica was discovered in 1928. . . . And we still have boxing,” Borland said. “Football will continue.” But those that take up the sport may change, he suggests, as the player pool becomes composed more of “impoverished inner-city kids that play these dangerous sports," a premise Borland credits to the work of Harry Edwards, a sociologist who has been a consultant to the 49ers.

Borland does see the sport as inherently dangerous. His fear of a degenerative brain disorder didn’t stem solely from a fear of concussions but rather the fundamental way the game of football is played.

“One thing that’s important to understand is that it’s believed that the pathology of CTE doesn’t have to do with concussion so much as it has to do with the accumulation of sub-concussive hits,” he said. “So every hit matters. If you’re subject to 800 or 1,200 of these every year, it accumulates. It’s like erosion.”

That’s why he prefers the term “repetitive brain trauma” to “concussion” when talking about CTE, finding it better reflects how the disease takes root. It also has implications for when players first take up the sport.

“I think it’s America,” he said. “You should be able to do what you want to do. I think with youth football, I think that’s another conversation. I don’t think you can make an informed decision at 5 years old, don a helmet and subject your brain to G-force hits.”

He has no children at this point, but, while he says he’s not anti-football, he knows he could face a future decision about whether to allow his child to play.

“I get that question a lot,” Borland said. “I think certainly waiting until high school [is appropriate]. I don’t think you miss anything, even if your goal is to be a great football player. . . . But I’d be surprised if my child played football.”

The scene he watched in May, teenagers colliding headlong, with real competition still four months away, is also why Borland is skeptical of the effectiveness of safety programs, such as the NFL-promoted “Heads Up.”

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“[Those programs] sound good in practice, but in reality, you drive by the high school and the coach is yelling, ‘Be tough!’ And they hit each other in the head,” Borland said. “That’s high school football.”

Borland calls on football leagues at all levels to do as the Ivy League has done and eliminate full-contact hitting from practices. The NFL has taken steps to curb practice-field hitting year-round (under provisions of the labor deal with the players’ union), in addition to strengthening concussion-treatment protocols and making certain hits illegal. Borland calls the professional version of the game “about as safe at the NFL level as it can be while staying football, without dramatic changes of eliminating the three-point stance or things like that.”

But safe is a relative term.

“The game happens extremely fast, a quarter-second difference,” Borland said. “You’re running 12 miles per hour. Your opponent’s running 15 [mph]. There are so many variables. I think it’s naive to suggest that you can throw a flag on the occasional hit where helmets collide and that’ll solve anything. . . .We talked about the accumulation of sub-concussive hits. How are you going to stop a guard from double-teaming down on a defensive tackle or a fullback blocking out on an end? That’s just football. That’s the game. So I’m sorry I don’t have a great answer for you. I think it remains inherently dangerous.”

As to whether the current focus on CTE, player health and additional measures to protect players will damage the league’s popularity, however, Borland defers.

“That’s above my pay grade,” Borland said. “I’m just an intern.”