LONDON – Calais Campbell’s face was flush with conflicting emotions as he listened to the question. He nodded his head in a manner that simultaneously connoted acknowledgement and horror.

Yes, he was saying, despite traveling all the way over here Thursday with his Jacksonville Jaguars teammates, he had heard that medical researchers found stage 3 CTE in the brain of deceased New England Patriot Aaron Hernandez. And yes, Campbell was indicating without words, a sad cocktail of depressing, alarming and terrifying.

“Scary,” Campbell said simply. “Very scary.”

Every NFL player knows about CTE, about concussions, about brain trauma. They’ve all heard the stories of old players unable to cope, living in their trucks, drowning their pain in pills or pints or even in select cases killing themselves rather than try to carry on.

Every NFL player fears it. They play anyway.

“As a football player,” Campbell said, “one thing you want to do is take care of your brain.”

Hernandez was just 23 when he stopped playing in the NFL. He wasn’t some old guy from another generation. He didn’t have 16 some-odd seasons under his belt. He was a young man, just 27 in May when he hanged himself with a bed sheet inside a maximum-security prison in Massachusetts, where he was serving a life sentence for murder. He had been charged in two other homicides, among other violent outbursts. His life, once so promising with a $40 million contract to catch Tom Brady passes, had become a pathetic, penned-up existence.

No player thinks football is going to turn him into a murderer. And there is no proof that football did that to Hernandez. It could have been any number of things, or a mix of all of them. Maybe his suicide wasn’t because of CTE but because he was never getting out of prison.

Besides, Hernandez is but one player of many, the vast majority of whom are living happy, healthy, productive post-football lives.

Still, the details in Boston University’s study of Hernandez’s brain were chilling. Hernandez had “advanced stage” CTE, commonly found in players with a median age of “67 years old”, according to a lawsuit filed on behalf of Hernandez’s young daughter against the NFL and the Patriots. The suit blamed the league and team for not identifying it earlier and preventing his eventual suicide.

Whether the lawsuit stands a chance is a separate topic. In the NFL, the focus was solely on the CTE report.

“Yep,” Campbell said. “That is getting discussed in every locker room.”

Campbell is 31, eight years older than Hernandez when his career ended due to arrest. He has played in 149 NFL games to Hernandez’s 44. He competes with similar reckless abandon, a towering defensive lineman with 60.5 career sacks, including four this season. He came to Jacksonville after nine years in Arizona, where he reached two Pro Bowls.

Like everyone in the league, he knows what he willingly signed up for – and is paid handsomely to do. That doesn’t mean the news doesn’t hit like a punch to the gut.

“It’s tough, you want to balance the risk but enjoy the benefits of the game,” Campbell said. “I love football. It’s changed my life. I’ve been a fan since I was 6 years old. If I wasn’t playing in the NFL, I’d be a fan. I want to find a way to play the game in a safe manner because it’s such a fun game.”

He points to the intangible benefits; a life of learning the value of teamwork and hard work, of sacrifice both shared and solo.

“There are so many good things it can teach you about life,” Campbell said. “You just want to make it as safe as possible.”

If anything, he says the game and the NFL itself have made so much progress. He likes the new on-field rules, even if it makes sacking quarterbacks more difficult. Technology has made helmets safer. The collective-bargaining agreement has limited full contact practices. And even on individual levels, players seek better health, everything from how they handle concussions to focusing on tackling with better form.

He was speaking on a sunny Friday afternoon from the stadium of Saracens RFC, a powerhouse rugby team here. Campbell, an avid reader, chess enthusiast and travel buff, discussed how he has become a big fan of rugby and studies the style because of the way they tackle stresses technique rather than simple blunt force.

[Watch on Yahoo: Ravens vs. Jaguars live from London Sept. 24]

“I see some brutal hits in that game, but if you do it the right way it’s a lot of fun,” Campbell said. “You see youth football changing the rules to make the game a lot safer as well. Hopefully kids will develop into better football players with better technique.”

That’s the present and that’s the future.

The past is always out there for these guys, though, hovering behind them, like a shadow they can never fully shine away. No one knows how a brain reacts to trauma, or what even counts as trauma in the first place. Why him? Could it be me?

There is no sign of regret in Calais Campbell’s voice. There is that unbending sense of concern, or at least respect though, that this is a dangerous business.

Aaron Hernandez’s CTE diagnosis managed to assure that, managed to rock every locker room in the league, perhaps college and high school football as well.

Football is a spectacular sport. It can also be scary. Very scary.

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