For more on concussions and their impact on and off the playing field, watch Dr. Sanjay Gupta's full report, "Head Games: The Truth about Concussions," on "Sanjay Gupta MD" Saturday and Sunday at 7:30 a.m. ET
(CNN) -- Former NFL quarterback Kurt Warner knows how it feels when a 250-pound defender is charging after him on the playing field. He knows the frenzied scramble, the attempt to evade a defender. Warner also knows, when none of that works, how it feels to have 250 pounds of flesh crushing him.
It is an understatement to say that during his 12-year career Warner was battered. He suffered a handful of concussions and countless hits. Yet through everything, Warner was determined to keep playing. It is an attitude that is fundamental to football culture, he said.
"There's always a big push from an organization and coaches because obviously that's their livelihood and they want their best players out there playing," said Warner, who retired earlier this year from the Arizona Cardinals.
"I don't think anybody came up to me and said, 'Well you have to play whether you're 100 percent or not, we need you.' Nobody said anything like that. But you wondered if guys were looking at you a little differently and saying ... he's not being tough," Warner said.
Playing tough includes playing through concussions.
"I think a lot of guys when they get, you know those hits or those concussions they think, 'OK well I'm just going to kind of play through it here for the short term and it's going to get better,' " said Warner. "I would venture to say probably 100 percent of the guys that played my sport in the NFL have been there."
Dr. Richard Ellenbogen, co-chair of the NFL's Head Neck and Spine Medical Committee, said the league is working to shift that culture. The NFL recently implemented new rules regarding when players can return to play.
"If anything, we are going in the other direction, where people sit out until they are totally symptom-free," said Ellenbogen, who is also the team physician for the Seattle Seahawks in Washington. "There are so many protocols now. If a guy gets pulled out in a game he cannot go back until he's cleared by the team doctor and an independent neurosurgery or neurology consultant."
The issue is layered, but critics suggest that the concussion problem at the NFL level is two-pronged. Players, afraid of losing coveted time on the field, may feel compelled to hide their symptoms. At the same time, the league places a premium on winning.
"I've been listening to all of the focus on concussions lately," said Dr. Bennet Omalu, a forensic pathologist who studies the long-term effects of repeated blows to the brain. "We need to set the facts straight. Otherwise we will keep wallowing in complete confusion."
Omalu is co-director of the Brain Injury Research Institute. In 2002 he was the first to describe chronic traumatic encephalopathy (CTE) in American football players. He was finding brain damage in young players with a history of concussion.
The damage closely resembles dementia (usually diagnosed late in life) and is associated with a range of problems, including memory loss, rage, uncontrollable depression and suicidal tendencies.
According to Omalu, the issue with football, and consequently, cases of CTE, is not just concussion but repeated blows to the head -- an issue that would be unavoidable during a football game.
"For every documented concussion there are hundreds of impacts to the head called sub-concussions," said Omalu. "Players wouldn't have immediate functional impairment with sub-concussions."
The answer to those invisible injuries, said Omalu, is a conservative approach to blows to the brain. He added that he considers the NFL's current policy regarding return to play to be too permissive.
"When a player fractures his leg in a football game he is kept out of the game for three months," said Omalu. "A concussion is similar to a fracture. It damages brain cells. Don't you think it's counterintuitive if you keep a player out for months for a leg fracture that you would do the same for a person who sustains a fracture of their brain cells?"
Omalu said that under current NFL policy, CTE will be "epidemic." He said he has written to the NFL about shifting its policy so that players who exhibit concussion symptoms are held out of the game for three months, to allow time for the brain to heal. He has also lobbied the league unsuccessfully for research money.
"I strongly disagree with keeping any athlete out months without objective evidence of a cognitive or structural brain damage," said Ellenbogen. "If an athlete returns to baseline functioning without symptoms and has a normal neurological exam, neuropsychological testing and MRI, what is the evidence that keeping them out longer does anything? ... That three-month statement seems arbitrary and lacking in scientific data."
Omalu's view would be considered controversial among other researchers in his field, but he echoes a feeling among many outside the sport that football may be due for a cultural shift.
Warner, from his new vantage point outside the NFL, agrees.
"I think it's going to take a whole culture change from top to bottom to say our No. 1 priority is the player," said Warner. "I think it really needs to be something that the groundwork is laid and everybody understands that's the No. 1 thing. That it's not money and it's not how far you go in the playoffs."