BOSTON (AP) — Atlanta Falcons linebacker Tommy Nobis seemed to transition easily into his post-playing career, landing a job as the manager of the team’s training camp hotel and rising through the franchise’s front office to vice president.

For three more decades, the man who came to be known as “Mr. Falcon” never left football.

And football never left him.

“Growing up, I remember my mom having to call his secretary when he was going out to training camp to let them know what kind of mood he was in. And then vice versa,” his daughter, Devon Jackoniski, said in a recent interview with The Associated Press.

“We were pretty uneasy growing up,” she said. “Although my dad had just some beautiful moments of being a wonderful man, emotionally he was so unstable it was just hard to get close to him.”

Researchers have confirmed what Nobis’ family long suspected: He had the most severe form of chronic traumatic encephalopathy, the degenerative brain disease linked to repetitive blows to the head that can cause the kind of violent moods they had grown accustomed to.

And now, as the NFL world descends upon Atlanta for Sunday’s Super Bowl, it serves as a somber reminder of the impact that football can have on its players and those who love them.

“That truly was my dad’s first love,” Jackoniski said. “He wasn’t born with a lot of money. They were from a blue-collar area. It gave my dad a lot of opportunities, so it’s kind of a bittersweet thing.

“He told me before he became very ill he would never turn his back on football or do anything different. But he would educate kids a little different in the game,” Jackoniski said. “There’s something very wrong with slamming your head against a brick wall over and over and over again.”

A two-way star at Texas whose No. 60 was retired by both the Falcons and the Longhorns, Nobis won the Maxwell Award as the best all-around player in college football and finished seventh in the 1965 Heisman Trophy voting, just ahead of Bob Griese and Steve Spurrier. In the Orange Bowl against Joe Namath and top-ranked Alabama, Nobis led a goal-line stand to preserve the Longhorns victory.

He was the No. 1 overall pick in the 1966 NFL draft — the first ever selection by the brand new Atlanta Falcons franchise. Rookie of the year. Five Pro Bowl selections. But he never made the playoffs, with the upstart franchise posting only two winning records in his 11 seasons.

And when the Falcons reached the Super Bowl two years ago, he was too far gone to understand what it meant.

Dr. Ann McKee, the director of Boston University’s CTE center, said on Monday that Nobis had the most severe form of the disease, showing a “severe loss of neurons and large CTE lesions throughout the cerebral cortex.”

The family was not surprised.

“We knew there was going to be something wrong on his pathology report,” said Jackoniski, who is a physician’s assistant. “But it was shocking how a human being could still be alive with that little functioning brain.”

Jackoniski was 2 when her father retired from the NFL, but football was never far from their life.

Nobis spent three decades in the team’s front office, working in scouting, marketing, player development and corporate development. (He also ran a charity that provided job training for people with disabilities.)

She remembered her father, who died in 2017 at the age of 74, as a humble man who was not very social, and yet a great public speaker. A prankster. Big Red. Huckleberry Finn with Muscles.

He was beloved in Atlanta; Jackoniski said he would approach children with disabilities at restaurants, just to make them laugh.

With his family, Jackoniski said, Nobis was a disciplinarian. Aggressive. Intense. “We always said we had to walk around eggshells with my dad,” Jackoniski said.

CTE, which can only be diagnosed after death, has been found in more than 100 former NFL players, and in dozens more athletes and members of the military who have been exposed to repetitive head trauma. The disease can lead to memory loss, depression and even suicide.

“I don’t know that I ever saw my dad without showing signs of CTE, my entire life,” Jackoniski said. “In hindsight, I think that was the saddest part of the news. His children never even knew who he was. My mom even may have not known.”

Jackoniski said she doesn’t watch a lot of football any more, but she will watch the Super Bowl “just because I know it will be on in our house.” In an email follow-up to the telephone interview, she said she struggled to comprehend what the sport has meant to her family.

“Football was my father’s life, the air he breathed and therefore the air we breathed,” she wrote. “It brought discipline and recklessness, self-worth and depression, strength and weakness, determination and fear, teamwork and destruction of relationships, competition and dissension, friendships and loneliness, strategy and brutal honesty, entertainment and subsistence.

“In the end,” she said, “it brought humility in every sense of the word.”