The following is an excerpt from Chapter 15 from "JUNIOR SEAU: The Life and Death of a Football Icon," by Jim Trotter.

On March 2, 2012, NFL officials accused the New Orleans Saints of running a program that paid illegal bonuses to their players for injuring or knocking opponents from games. The allegation shook the league to its core. It already was on its heels from being sued for allegedly hiding the long-term dangers of concussions from players, so the notion that Saints coaches and management were directing and sanctioning a "bounty" program that paid out $1,500 for a "knockout" hit and $1,000 for a "cart-off" hit was both a PR nightmare and a potential legal land mine - particularly at a time when Commissioner Roger Goodell was pushing for increased enforcement of player safety rules.

Within locker rooms, players scoffed at the suggestion of a pay-to injure program. NFL players believe they are part of a brotherhood, and while they willfully and violently attack each other on Sundays, the idea of intentionally jeopardizing a family member's livelihood for a few extra dollars was revolting to most of them. Players were known to pool monies and reward teammates for big hits and big plays, such as sacks, interceptions, and forced fumbles. But that was a far cry from compensating someone for attempting to -- and succeeding at -- injuring an opponent.

Junior was two and a half years into retirement when the scandal broke. The suggestion that a player would intentionally seek to injure an opponent caused him to shake his head.

"That's some underground market they've got going on if it's true," he said. "I've never heard of anything like that. If it's true, it's the wrong thing to do. The way I played the game was to inflict pain on my opponent and have him quit. It was never to get paid for getting him out of the game. You should never incentivize anyone's health in the game of football. That is wrong. But to strike your will on another player in hopes that the player quits on you and allows you to do what you need to do at your pace -- that's the name of the game, to have your guy surrender. And once he surrenders, you don't stomp on him; you go on to the next guy."

Imposing his will often meant jeopardizing his health.

For instance, in a game late in his career with the Patriots, he broke his hand making a tackle near the end of the second quarter. At halftime he was sitting in the locker room with a bag of ice on it when a trainer approached.

"We need to go for an X-ray," the trainer said.

"Why?" Junior said, then added with a chuckle, "I know it's broke. We don't need to X-ray it."

Then he went out and played the second half without complaining or making an excuse.

Playing through pain is expected in the NFL, where the men are so big and fast, and the collisions so fierce, that it is easy to believe, as Arizona quarterback Carson Palmer once told Sports Illustrated, that "somebody is going to die" on the field. More frightening than the players' willingness to play through pain is the frequency with which they're willing to play through injuries, even if they know long-term consequences are possible.

In 2006, Washington Redskins outside linebacker/defensive end Jason Taylor was leg-whipped by an opponent and sustained a deep and painful calf bruise. He didn't know the true severity of the injury because it was masked by the Toradol injection he received before the game and the pain meds and prescription sleeping pills he took after it. Reality set in at 2:00 AM when the drugs wore off.

"He noticed that the only time his calf didn't hurt was when he was walking around his house or standing," Dan Le Betard wrote in the Miami Herald. "So he found a spot that gave him relief on a staircase and fell asleep standing up, leaning against the wall. But as soon as his leg would relax from the sleep, the pain would wake him up again. He called the team trainer and asked if he could take another Vicodin. The trainer said absolutely not ... The trainer rushed to Taylor's house. Taylor thought he was overreacting. The trainer told him they were immediately going to the hospital. A test kit came out. Taylor's blood pressure was so high that the doctors thought the test kit was faulty. Another test. Same crazy numbers. Doctors demanded immediate surgery. Taylor said absolutely not, that he wanted to call his wife and his agent and the famed Dr. James Andrews for a second opinion. Andrews also recommended surgery, and fast. Taylor said, fine, he'd fly out in owner Daniel Snyder's private jet in the morning. Andrews said that was fine but that he'd have to cut off Taylor's leg upon arrival. Taylor thought he was joking. Andrews wasn't. Compartment syndrome. Muscle bleeds into the cavity, causing nerve damage. Two more hours, and Taylor would have had one fewer leg."

When asked his reaction to the news, Taylor told Le Betard: "I was mad because I had to sit out three weeks. I was hot. Players play. It is who we are. We always think we can overcome."

Junior Seau, who was inducted in the Hall of Fame posthumously in 2015, finished his career with 1,522 tackles and 56.5 sacks. AP Photo/Greg Trott

Steve Wisniewski, the Oakland Raiders guard who had fierce battles with Junior, was one of the league's orneriest players during a 13-year career that ended after the 2001 season. He refused to accept defeat from an opponent or an injury. During a game at Buffalo he suffered a blow to the head that prevented him from standing upright on his own. He refused to leave the field, though, relying on teammates to hold him up until they broke the huddle for the next play.

"When Jeff Hostetler, our quarterback, called the play, I would turn to a buddy and ask, 'Is that a run or a pass?' " Wisniewski said. "I completely blanked on the scheme. But it was a different culture then. In that time period, you were really looked down upon if you couldn't be out there. If you were injured, you found a way to play. I missed one game in my NFL career. A second game I was dressed and my coach wouldn't let me play because I was literally hobbling. A great many times you're in the locker room wondering, How am I going to get through this game?

"I liken it to the military. I haven't served in the military, but my father, my brother, my son, my brother-in-law, my uncle -- they all served. In the military guys do extraordinary feats of heroism because of their buddies, for the people in their unit. They don't do it for heroism or country or politicians. They do it for each other. When I played I always had that sense that you're not going to let your team down. Junior was that way. He pushed himself. He was there for the team." The desire to be accountable sometimes causes players to self-medicate. Although the behavior is dangerous and potentially life-threatening, the risks are considered acceptable to some players because the rewards -- real and perceived -- are so great.

How do the players get the drugs? First, they hoard team-issued painkillers over time for fear they won't be able to get them from the club at a later date. Then some will barter the unused meds for stronger prescription drugs from teammates.

Say you sprain an ankle and receive 10 Vicodin from the club. If you have a high pain threshold, you might use only three and store the rest in the medicine cabinet. A few weeks later you break a finger and are given 10 more Vicodin, of which you use only five. Intentional or not, you now have an excess of powerful pills to use when and how you please, with no medical supervision.

"There were some practices that you could consider abusive when it came to the use of prescription meds," said Terrell Fletcher, a running back who played in 111 games for the Chargers from 1995 to 2002.

"Fortunately for me, I did not see any team officials assist with that, but it's not hard to do. People are in pain, guys want to get on the field and play, and sometimes you have to do what you have to do to try to keep yourself on the football field."

Each team's medical staff is required by law to log the painkillers that are administered to players, but there's no way for them to ensure that the pills are taken in full or as prescribed. There's also the issue of players who lie about the severity of their injuries, claiming after the prescription has lapsed that they're still in pain so they can stockpile meds for future unsupervised use.

"Self-medicating is very scary, but it does happen," said Fletcher. "When you're given anything unlegislated, it can be dangerous."

The NFL constantly contends with the perception that there's a conflict of interest when players are treated by doctors paid by the club. The thinking is that clubs need players on the field to win games and sell tickets, so they're going to do what's in the best interest of the franchise short-term rather than what's in the best interest of the player long-term.

In 2014 more than 750 retired players filed suit against the NFL, alleging that it put them at risk by routinely and illegally providing them with prescription pills and painkillers to keep them on the field. The 87-page complaint, filed in US District Court in San Francisco, states that the NFL "has intentionally, recklessly and negligently created and maintained a culture of drug misuse, substituting players' health for profit."

"To strike your will on another player in hopes that the player quits on you and allows you to do what you need to do at your pace -- that's the name of the game, to have your guy surrender. And once he surrenders, you don't stomp on him; you go on to the next guy." Junior Seau

Marcellus Wiley, a defensive end who played for Buffalo, San Diego, Dallas, and Jacksonville, joined the lawsuit in June 2014 after suffering partial renal failure in April, despite no history of kidney problems. During one season with the Chargers, Wiley was diagnosed by team physician Dr. David Chao as suffering from a severe groin strain. He was treated with "multiple injections" of painkillers throughout the season to cope with the condition.

Following the season, according to Wiley, an independent doctor diagnosed a torn abdominal wall that required surgery.

"You can't walk into a doctor's office and say, 'Give me this, give me that, just to get through the day.' Somebody would shut the place down," Wiley told ESPN.com. "But that's what was going on in the NFL. It's easy to get mesmerized, I won't deny that. There's this 'playthrough- the-pain, fall-on-the-sword' culture, and somebody in line ready to step up and take your place.

"The next question when people hear about this stuff is: 'Where's the personal responsibility?' " he continued. "Well, I'm not a medical doctor, but I did take the word of a medical doctor who took an oath to get me through not just one game, or one season, but a lifetime. Meanwhile, he's getting paid by how many bodies he gets out on the field." Dr. Chao stepped down as the Chargers' team physician in June 2013.

Wiley spoke to the culture of the NFL in 2003, while playing for the Chargers and doing a weeklong, first-person series with the Los Angeles Times.

"Sometimes you need a fistful of Vioxx. Any anti-inflammatory. You need it to survive," he was quoted as saying. "Vioxx is a beast. I love Vioxx. I'm going to invest in that company when I retire. When you get a shot of painkiller, it's not like when they're taking blood at a blood bank. They've got to grind that needle in there. I mean grind it. When you've got an injury and it's acute, they've got to go get it. They can't just shoot you up on the surface. The guys laugh at me because I'm in tears when I have to get one. I bite on a towel and just try not to pass out. I hate shots. I've fainted on shots before, so anything like that kills me. ... After you get it, there's some numbing and there's a placebo effect. You know it's doing something so you feel better already. I probably don't want to know what they're shooting in there, but it's probably some kind of anti-inflammatory. It's like a fire extinguisher. Something's on fire inside of you, and they've got to get that extinguisher in there to put out the flames."

The pressure to play often is more internal than external. Players want to be there for their teammates and will try to play through anything, even concussions. It's one reason Junior was supportive of Goodell's push, beginning around 2010, to make the game safer by imposing stiffer fines and penalties -- and in some cases suspensions -- for hits to the head of defenseless receivers and quarterbacks.

Junior felt that players needed to be protected from themselves, a point that was driven home by his own career. He played in 268 games over 20 seasons, had more than 1,400 tackles, and administered and absorbed countless collisions. Yet he never was diagnosed with a concussion. That's not to say he never sustained one, because he did. Many of them.

"I can't even count how many," said Gina. "After games, particularly away games when I would watch them on TV, we would talk about the game and how he played. Sometimes I would ask him what happened on a certain play or why something went wrong and he wasn't in a certain spot. He would say, 'Oh, I had a concussion. I just had to shake it off.' "

That type of thinking and attitude was common before concussions became a national conversation around 2010. Prior to that, players, coaches, and team executives rarely used the term. Instead, they relied on euphemisms. It was common to hear things like, "He got his bell rung," or, "He got dinged." Ironically, many players considered it a badge of honor to be concussed. Junior referenced it in an early 1990s NFL Rocks: Extreme Football 2 video.

"When you put on a good hit, it hurts you too," he said. "This game is a matter of inflicting pain on the other person. It's an ego thing. If I can feel some dizziness [after a hit], I know that guy is feeling double of what I feel. So, yeah, the hitting that I put on somebody else is always going to be judged by how I feel going back to the bench."

It is only in the last five to 10 years that the public has begun to understand the connection between concussions and dementia, memory loss, and depression. The NFL tended to pooh-pooh, sidestep, or dismiss any suggestions of a link before then. Sometimes it went so far as to shoot down its own studies. For instance:

"In 2009, the NFL funded a University of Michigan study that showed that former players between 30-49 were 19 times more likely to have Alzheimer's and other mental disorders than men of the same age," ESPN.com wrote. "But the league disavowed the study, saying that it did not specifically study dementia and was based on unreliable phone surveys."

Junior Seau played for the Chargers, Dolphins and Patriots over 20 NFL seasons. Scott Boehm/Getty Images

Nate Jackson played tight end in the NFL from 2003 to 2008, and after each season he would save his helmet. When talk about a possible link between repeated brain trauma and long-term health consequences grew from a murmur to a whisper to a shout, he began studying the helmets. To the rear bottom of one earhole was a small, clear sticker that featured tiny print. It read:

WARNING: NO HELMET CAN PREVENT SERIOUS HEAD OR NECK INJURIES A PLAYER MIGHT RECEIVE WHILE PARTICIPATING IN FOOTBALL. Do not use this helmet to butt, ram, or spear an opposing player. This is in violation of football rules and such use can result in severe head or neck injuries, paralysis or death to you and possible injury to your opponent. Contact in football may result in CONCUSSION-BRAIN INJURY which no helmet can prevent. ... Ignoring this warning may lead to another and more serious or fatal brain injury.

The scary part for Jackson was that no trainer, doctor, or coach had ever spelled out said dangers to him -- or even notified him or his teammates about the sticker and its warning. In fact, the league and its TV partners glorified the violence and big hitters of the game, featuring them in commercials, video games, and highlight material.

That sort of behavior was at the heart of a 2011 class-action lawsuit in which more than 4,500 former players claimed that the NFL hid from them the dangers associated with concussions. The case was filed six months after Dave Duerson, a former safety with the Chicago Bears, put a gun to his chest in his Sunny Isles Beach, Florida, home and pulled the trigger - but not before leaving a note asking that his brain be examined by the Boston University School of Medicine.

BU scientists discovered that Duerson was suffering from chronic traumatic encephalopathy (CTE), a degenerative brain disease that's triggered by repetitive trauma to the brain. Each trauma produces a buildup of an abnormal protein called tau, which causes the brain degeneration associated with memory loss, confusion, impaired judgment, impulse control problems, aggression, depression, and, eventually, progressive dementia. Typically, the first symptoms present themselves years or even decades after the trauma occurs or an athlete stops playing and involve issues with judgment, reasoning, problem solving, impulse control, and aggression.

Duerson, who played for the Bears, Giants, and Cardinals over an 11-year career, was known to be suffering from depression and other neurological problems. His death took on greater significance 14 months later when Ray Easterling, a 62-year-old retired safety who had played for the Atlanta Falcons, shot himself to death at his home. Easterling not only was known to be suffering from depression, insomnia, and dementia but also was the initial plaintiff in the classaction suit against the league.

The suicides of these players, combined with mounting scientific research on the dangers of repeated brain trauma, put the league on the defensive. Over a four-year period, Commissioner Goodell made player safety during games a point of emphasis, penalizing, fining, and even suspending defensive players who hit opponents above the shoulders. He also moved the kickoff up five yards, to the 35-yard line, in hopes of decreasing the speed and violence of the collisions that occur on the play. And for the first time, the league placed independent neurologists on the sideline during games and created uniform protocols that had to be met before a player could return to the field after sustaining a concussion.

All of this was done with an eye on protecting the players, the league said, but cynics wondered if the real reason was to protect the golden goose. With revenues soaring past $10 billion annually, the last thing owners wanted was more litigation that could scare away fans and sponsors. The league was at a point where it could no longer deflect and deny the link between brain trauma and neurological health issues.

In fact, as part of its $765 million settlement agreement in the classaction suit, it submitted documents that said its players were likely to suffer chronic brain injury at a "significantly higher" rate than the general population and also to show neurocognitive impairment at a much younger age. The documents said retired players between 50 and 59 years old developed Alzheimer's disease and dementia at rates 14 to 23 times higher than the general population in the same age range. They also stated that the rates for players between 60 and 64 were as much as 35 times the rate of the general population.

More damning, the PBS show Frontline reported in September 2014 that the Department of Veterans Affairs' brain repository had found CTE in 76 of the 79 former players it examined, including Duerson.

Excerpt from "JUNIOR SEAU: The Life and Death of a Football Icon," by Jim Trotter. Copyright © 2015 by Jim Trotter. Used by permission of Houghton Mifflin Harcourt. All rights reserved.