Junior Seau's death felt different.

The reaction to another apparent suicide by an ex-NFL player seemed deeper, more immediate, less of a formal acknowledgement of "that's very sad" and more of an emotional, pit-of-the-stomach response from fans, reporters and players alike.

Unlike Andre Waters and Dave Duerson, who was each more than a decade removed from their playing days when they took their own lives, Seau played as recently as 2009. He was a Pro Bowler as recently as 2002. Even very young fans know of Seau and watched him. Some of his teammates and contemporaries are still in the spotlight, and their pained reactions put a very public face on the grief of those who knew the former linebacker.

Eagles linebacker Casey Matthews wrote on Twitter that he wore 55 in college in part because he so admired Seau. Patrick Willis called Seau "1 of the most impactful Lb's to ever play the game." This isn't a case of a player whose glory has faded to memory. This is a man who most of us remember watching and who appears to have shot himself in the chest at the age of 43.

Seau's death feels like a moment when the growing concern about the long-term effects of head injuries in football gains traction with a much wider audience. Whether or not brain trauma had any impact on Seau specifically, many now link athletes' suicides to the blows to the head they endure during their playing days. That growing perception is the biggest cloud looming over the NFL and its dominance of the American sports landscape. It has the potential to change the way at least some view the game and its place in our culture.

"The side effects of head trauma are a serious issue that can not be ignored," Eagles guard Evan Mathis wrote on Twitter. "Junior Seau's death will bring the topic into the spotlight."

Mathis took a small leap, since we don't know what led to Seau's apparent suicide, but he was saying what was on the mind of anyone who has paid attention to the mounting evidence of the dangers of playing football. We're still waiting for more facts about Seau's specific case, but the overall perception is important and affects how people who support the NFL view the  game.

Let's be clear here: no one knows right now if head trauma played any role in Seau's death. I wrote that today. The condition that afflicted players like Duerson and Waters – chronic traumatic encephalopathy -- can't be diagnosed until after death. Even if Seau suffered from CTE, doctors caution that they have not established a direct link to suicide. Many ex-football players live through concussions and enjoy full lives after retirement. People who commit suicide do so for a variety of reasons. Sports Illustrated's Peter King reported today that Boston University doctors who have done significant research on former athletes' are trying to acquire Seau's brain.

But when it came out that Seau had shot himself in the chest, it was impossible not to think of Duerson, who also killed himself with a shot to the chest and asked that his brain be sent to the doctors in Boston. He was found to have CTE, same as Waters. So was ex-Steeler Mike Webster, a Hall of Famer who spent much of his later life sleeping on the floor of an Amtrak station. Ex-athletes, after once embodying the peak of physical performance, have been found to have brains in their 40s and 50s that resemble those of people in their 80s.

There might not be a scientific connection, but in the minds of the fans who prop up the NFL and who decide if their children should play football, the mounting anecdotes are becoming hard to ignore.

I spoke today to Tom Thomas, whose son Owen was a Penn lineman who hanged himself in 2010. He was a college junior, 21, and was later diagnosed with CTE. Tom Thomas, too, had played football. He was a fullback at guard at the University of Virginia. He has registered to have his brain studied at Boston University after he dies.

When doctors there looked at Owen's brain, they found evidence of CTE, which shows up in the form of proteins that build up in the brain. According to the Sports Legacy Institute, it can lead to memory loss, confusion, impulse control problems, impaired judgment, aggression and depression.

Tom Thomas said his son always took academics seriously, but was frustrated at Penn when he couldn't seem to keep up.

"I think for Owen, that compromised ability, which he didn't understand why, must have been so frustrating for him. Why he couldn't concentrate, why he couldn't focus, why he couldn't do these things," Thomas said. "It wasn't until the day before he died that he expressed in a phone conversation frustration," about school.

But did the CTE lead to Owen's suicide?

"I think it was a contributing factor, I don't think it was the only factor," Thomas said. Someone who put less pressure on himself, for example, may have reacted differently. "I do think it affected his impulse control."

One of the frightening things about Owen's case, though, is that he was never diagnosed with a concussion. Doctors believe that it doesn't take an injury that severe to contribute to CTE. Even sub-concussive blows, accumulated over time, might do it. Those are the kinds of blows we see on every play and every practice in the NFL, when offensive and defensive linemen collide at the snap. In training camp it happens day after day after day. It's an inextricable part of the game and the culture of football, and it may have worse consequences than we know.

Again, there are unknowns. CTE doesn't seem to have long-term impacts on every player who leaves the game, only some. But it's enough of a concern that more than 1,000 players are suing the NFL, accusing the league of downplaying the effects of head injuries for years before it got serious about concussions. The league strongly contests the claim.

Who is right and wrong legally will play out in court and between lawyers. Professional players are adults making their own decisions, and they make a lot of money and gain great fame playing a game they love.

But fans and writers are not just bystanders.

When I wrote about the concussion lawsuit in February, it got relatively little reaction here on Philly.com. People prefer to talk about moves their team is making. I get that.

But I wondered, what if it was Brian Dawkins, not Andre Waters, who served as an example of the devastating effects of CTE and the vicious hits safeties deliver every Sunday? Would fans have as muted a reaction then? Or would there be more soul-searching if the person affected was a hero whose jersey many fans still own?

Seau's suicide seemed to answer that yes, people would pay more attention when the person involved is a recent player, a fixture whose playing days we can still easily recall.

It's worth repeating: no one knows if Seau suffered from brain trauma or if it had any effect on his decision to kill himself. (Though just because he was never "listed" with a concussion means little, since you don't necessarily have to have one to suffer CTE and unreported concussions aren't exactly a rare phenomenon).

What's clear, though, is that history and a growing body of medical evidence says that at least some of the players we cheer and write about on Sundays will spend later stages of their lives facing debilitating problems such as drug abuse and depression; that some of their brains will age well before their time and that some will leave behind the glories of their 20s for misery in their 50s. If you actually look, it's a grim picture for some.

What do we do with that information? Does it change the way we respond when the NFL cracks down on hits to the head? Does it change whether parents let their children play football? Does it change how we react when a player such as DeSean Jackson returns from a concussion? Will the focus be on what long-term damage he may have suffered, or whether he'll go strong over the middle?

Players make their own choices. This isn't about their decisions. This is about those of us who choose to watch and cheer and write. Do we act unaffected, even as the consequences become more and more obvious? Or do some fans turn away? Could it be enough that it dents football's standing as the king of American sports?

I don't know the answers. I grew up watching football every weekend and make my living writing about the sport. My weekends, like those of many fans, are built around 1 p.m. and 4 p.m. time slots. It is hard to beat the NFL for pure entertainment and there are many admirable stories to be found within the game. But there's something that doesn't sit quite right about seeing young men potentially take years off their lives and cheering because it's just so darn exciting. I'm not sure how to resolve it.

Over at Grantland, there have been theories that brain trauma could be the factor that cuts down the NFL. One thought was that the liability concerns and costs would eat away at high school and college programs and eventually the league. Another was that fewer and fewer children will take up the game. In either case, the grass roots that support the NFL would wither and eventually affect football at all levels.

To me, those ideas sound extreme. Then again, so is the evidence of the consequences of head injuries.