• The league in 2005 tried unsuccessfully to have medical journals retract the published work of several independent concussion researchers.

• Independent researchers directly warned Goodell about the connection between football and brain damage in 2007, but the commissioner waited nearly three years to acknowledge the link and to dismantle the league's discredited concussion committee. In 2009, two other independent researchers delivered still more evidence that football caused brain damage during a private meeting at the NFL's Park Avenue headquarters. Yet the league committee's co-chairman, Dr. Ira Casson, mocked and challenged the researchers so aggressively that he offended others who were present, including a Columbia University suicide expert and a U.S. Army colonel who directed the Defense and Veterans Brain Injury Center.

• As the crisis escalated, the NFL tried desperately to regain control of the issue and contain damage to its brand. Before an October 2009 hearing on football and brain injuries conducted by the House Judiciary Committee, the NFL lobbied successfully to prevent Goodell from testifying on the same panel as the father of a high school quarterback who had died after sustaining a concussion.

• Dr. Ann McKee, the leading expert on football and brain damage, told the authors that she believes the incidences of neurodegenerative disease among NFL players will prove to be "shockingly high" and that "most NFL players are going to get this. It's just a question of degree." Since 2005, when the disease was first diagnosed in deceased NFL players, McKee has studied 54 brains harvested from deceased NFL players. All but two had chronic traumatic encephalopathy (CTE). "I'm really wondering where this stops," she told the Fainarus. "I'm really wondering if every single football player doesn't have this."

The health of former players and the league's previous scientific exploration formed the basis of a lawsuit filed against the NFL by more than 4,500 ex-players. The players charged that the league's Mild Traumatic Brain Injury Committee conducted fraudulent research to hide the connection between football and brain damage. On Aug. 29, the NFL and the former players settled the lawsuit for $765 million.

Former longtime New York Jets defensive lineman Marty Lyons, who is being inducted into the team's Ring of Honor on Oct. 13, was asked Wednesday about the issue of whether the league downplayed the concussion issue.

"I'm not going to accuse the league. You'd come off to the sideline [during a game] and maybe they wouldn't use the words 'You got a concussion.' You got dinged. Many times, they'd say, 'How many fingers?' You'd say three, and they'd say, 'Yeah, that's close enough' and you'd go back in," Lyons told ESPNNewYork.com's Rich Cimini. "That was by choice. That wasn't doctors or trainers saying, 'You're OK.' They would tell you to sit on one side of the bench and they would go look at other players. Next thing you'd know, you'd be back out there on the field. Players had to be more responsible for their own actions. I'm not saying the league didn't know, I'm not saying the players didn't know. It was part of the game."

One of the most significant findings in the book, for which the authors say they conducted more than 200 interviews and reviewed thousands of pages of previously undisclosed documents, traces how the league handled research under Tagliabue's guidance.

In 1994, Tagliabue established the Mild Traumatic Brain Injury Committee to act as the league's concussions investigatory committee. According to the book, the committee published its controversial research in a medical journal, "Neurosurgery," that was edited by a consultant to the New York Giants. The Fainarus write that the consultant, USC neurosurgeon Dr. Michael Apuzzo, was a "sports guy wannabe" who frequently worked into conversations that he'd just had lunch with Tagliabue and was thrilled to stand on the sidelines during games.

Some of the studies the NFL had published in "Neurosurgery" had startling conclusions: Concussions were minor injuries; multiple concussions did not increase the risk of further injury; and football did not cause brain damage. "Professional football players do not sustain frequent repetitive blows to the brain on a regular basis," the NFL's doctors asserted, according to the book.

Often, the Fainarus write, Apuzzo ignored peer-reviewers' objections to the league research before rubber-stamping it into the journal. The actions led some concussion researchers to privately ridicule "Neurosurgery" as "The Official Medical Journal of the National Football League" and the "Journal of No NFL Concussions," the authors write. Apuzzo declined to be interviewed for the book; he also declined to be interviewed for this story.

Dr. Kevin Guskiewicz, a researcher who joined the league's new concussion committee after the NFL dismantled the MTBI group, rejected the "Neurosurgery" papers, which he described as "industry-funded research at its best," according to the book.

Dr. Mark Lovell, who directed the NFL's Neuropsychological Program for 16 years, told the book's authors that concussion committee leaders inserted provocative language in research papers after they had been read and approved by other members, including him. In one passage, Lovell called "stupid" a claim by league researchers that it was "unlikely that athletes who rise to the level of the NFL are concussion prone." He also said he did not write that sentence. When the Fainarus reminded Lovell that he was listed as an author, he replied: "No, no, no. I mean, is my name on that sentence?"

The book levels sharp criticism at the handling of the health and safety issue by Goodell, who succeeded Tagliabue in August 2006. The authors write that Goodell inherited a concussion mess from Tagliabue but that Goodell took nearly three years to acknowledge a link and moved slowly to publicly address the growing crisis.