TAMPA, Fla. — It's lunchtime and Charlie Garner sits in a restaurant near his home, looking and sounding like a man on top of the world.

He is 45 now, but he appears nearly as fit as he did during an 11-year career as an NFL running back. He says he still has a good chunk of the money he earned playing football. He is excited as he talks about the catering business he is starting in Northern Virginia, where he grew up. And, most of all, he talks with extreme pride about his two daughters and one son.

But, all of the sudden, it becomes horribly obvious all is not right with Garner. He is in the middle of a sentence when his sandwich drops from his hands to his plate for no discernible reason. His hands also fall to the table and don't move. The person with Garner looks at him with no idea what has just happened or how to react.

"This is friggin' serious," said Garner, who played for the Philadelphia Eagles, San Francisco 49ers, Oakland Raiders and Tampa Bay Buccaneers. "The doctors said this was going to start happening and now it's happening."

Garner sits motionless and silent for about two minutes. Then, his hands move and he starts talking again about the other things the doctors have been telling him. This is not a pretty story.

***

Doctors have told Garner they believe he has Chronic Traumatic Encephalopathy, which in recent years has become a plague for former NFL players. It can only be diagnosed post-mortem. But Garner is showing many of the symptoms. He's not afraid to admit he's scared.

"I don't have all my faculties anymore," Garner said. "I can't remember things. When I go to the mall or grocery store, I have to take one of my kids with me to remember where the car is parked. I have trouble remembering conversations I had five minutes ago. Bright lights bother me. I just don't feel right all the time."

As Garner ticks off the list of his symptoms, it becomes apparent they match up with many of the signs doctors say are associated with CTE.

MORE: Faces of NFL's head trauma crisis

HIPPA laws forbid Garner's doctors from talking about his condition. But Dr. Christopher Giza of the American Academy of Neurology and a professor at UCLA agreed to talk in general terms about the long-term impact of concussions.

When told of Garner's symptom's and history, Giza said they could be signs of CTE, but that he would not automatically make that diagnosis.

"Memory problems, headaches, light sensitivity and mood swings can be caused by many different things, most of which are treatable," Giza said. "So for patients with chronic symptoms and a history of head impacts/concussions, it makes sense to do a careful evaluation, objective neurocognitive testing, identify treatable problems and then initiate a multi-pronged treatment plan."

Garner said he has undergone extensive testing and believes he has CTE. Doctors say it can lead to dementia, depression and Alzheimer's disease. They also have speculated that it can lead to suicide.

The most famous case was that of former All-Pro linebacker Junior Seau. After his suicide, doctors said his brain showed signs of CTE. Dozens of other former NFL players have been diagnosed with CTE.

"I haven't had depression or anything like that," Garner said. "But it scares the heck out of me. The doctors say it could get worse. One doctor told me that if Muhammad Ali was up here (Garner said raising one hand as high as possible) and the average person is here (holding his other hand near the table), I'm right about in the middle. That didn't make me feel very good."

A former girlfriend of Garner's, who did not want her name used, said he exhibited extreme mood swings, which was the reason for their relationship's break-up about a year ago.

She said Garner was never physically abusive. But he was verbally abusive.

"He was a pussycat one minute and a lion the next. You just never knew when the volcano would erupt."

***

Doctors believe CTE is caused by repeated blows to the head. Garner said he came out of his career thinking he was safe. Officially, he said, he was diagnosed with only two concussions while playing in the NFL and none in college. But the symptoms started about a year ago. When he went to a doctor for the first time, he was shocked by what he heard.

"He explained that even minor collisions could cause the brain to rattle against the skull," Garner said. "When I thought about that, I realized I probably had at least a dozen concussions a year and played through them. You do the math. At least a dozen concussions a year over 11 years. No matter how you look at it, that's a lot."

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Giza wasn't surprised to hear Garner's statement that he had more than two concussions in his career.

"It's certainly likely than at athlete 10 or 20 or more years ago might have had undiagnosed concussions," Giza said. "Sometimes athletes feel symptoms and aren't aware that it might be a concussion, so they don't come to medical attention. Also, there is the possibility that for some head impacts, even without symptoms, might cause subclinical injuries that add up over time."

It wasn't until 2009, five years after Garner's career ended, when the NFL implemented its first concussion protocol. Just two years ago, the league enacted a rule in which an independent medical spotter could contact a member of the officiating crew if a player appeared to be having trouble.

"Speaking from personal experience, you’re in the heat of the battle, your adrenaline is running, you're taught to continue to compete — when ultimately, you need assistance or you may need help, just to be evaluated," former player and NFL executive vice president of football operations Troy Vincent told Sporting News at the time.

Garner says he joined the lawsuit by former players against the NFL for not educating them enough about the dangers of concussions. The suit was settled for a reported $1 billion. Still, he is proud of his career. He made the Pro Bowl and, in the 2002 season with the Raiders, had more than 900 yards rushing and receiving.

"Football gave me a good lifestyle for me and my family," Garner said. "But I might end up paying a big price for it. Other people already have paid a big price for it. People ask me all the time if I would do it all over again if I knew more about concussions. I say yes, but I would do it as a defensive back because I wouldn't have taken so many hits."

MORE: Notorious career-ending injuries

Garner's youngest child is Charlie, his only son. He's 10, and Garner calls him "C4" because Garner, his father and grandfather all were named Charlie. C4 is already showing uncommon athletic ability. He dominates his age group in basketball.

He also excels in seven-on-seven flag football, but he does not participate in contact football. Did his father make that decision?

"No, it's his choice all the way," Garner said. "He's old enough to hear some of the things about concussions. Maybe when he gets into high school, he might want to play. I won't stop him and I'll support him.

"But I'll encourage him to play defensive back and do everything I can to keep him safe. But, if he doesn't want to play, that will be fine with me."

Pat Yasinskas is a freelance writer based in Tampa. He previously wrote for ESPN.com, The Charlotte Observer and The Tampa Tribune.