Players' lawyer David Frederick also accused the league of concealing the emerging science about concussions over several decades, even after creating a Mild Traumatic Brain Injury committee in 1994.
"It set up a sham committee designed to get information about neurological risks, but in fact spread misinformation," Frederick argued at a pivotal federal hearing to determine if the complaints will remain in court or be sent to arbitration.
U.S. District Judge Anita Brody's decision could be worth billions to either side.
About 4,200 of the league's 12,000 former players have joined the litigation. Some are battling dementia, depression or Alzheimer's disease, and fault the league for rushing them back on the field after concussions. Others are worried about developing problems and want their health monitored.
A handful, including popular Pro Bowler Junior Seau, have committed suicide.
NFL lawyer Paul Clement insisted that teams bear the chief responsibility for health and safety under the players' collective bargaining agreement, along with others.
"The one thing constant throughout is these agreements put the primary role and responsibility on some combination of the players themselves, the unions and the clubs," Clement argued.
"The clubs are the ones who had doctors on the sidelines who had primary responsibility for sending players back into the game," he added at a news conference after the 40-minute hearing.
U.S. District Judge Anita Brody appeared most interested in whether the contract is sufficiently specific about health and safety issues to keep the matter in arbitration.
"The thing that concerns me is you say it talks about it 'all over,'" Brody said to Clement. "It has to be really specific. That's what I have to wrestle with."
Frederick said the contract is "silent" on latent head injuries, making the lawsuits appropriate.
Brody is not expected to rule for several months, and the cases could take years to play out if her ruling is appealed, as expected.
Players' family members on hand for the hearing included Kevin Turner, a former Philadelphia Eagles running back now battling Lou Gehrig's disease; Dorsey Levens, a veteran running back who made a 2012 documentary on concussions called "Bell Rung" and Mary Ann Easterling, whose husband, former Atlanta safety Ray Easterling, was the lead plaintiff in the litigation before he committed suicide last year.
Attendees might have momentarily thought they were on the playing field, as a power problem at the federal courthouse caused muggy conditions in the courtroom. The judge insisted that the well-heeled crowd of lawyers remove their suit jackets. Frederick did so, while Clement declined.
Both more typically find themselves at the U.S. Supreme Court, where Clement has fought gay marriage laws and state health care mandates, and Frederick has pursued consumer protection cases.
Their very presence signaled the importance of the litigation to both sides, on both a financial and public-relations grounds.