Quarterback Kevin Kolb #4 of the Buffalo Bills is hit after scrambling against the Washington Redskins in the first quarter during a preseason game in 2013.Patrick Smith/Getty Images

Football is America’s most popular sport and the NFL is the most profitable sports league in the world. But behind the curtain of the Big Game’s glitz and glamour is a league plagued by controversy, most notably the NFL’s refusal to acknowledge the correlation between football and brain damage. Mark Fainaru-Wada, ESPN reporter and co-author of the book “League of Denial,” which chronicled two decades of the league’s malfeasance on the issue, said he was struck by the NFL’s profound level of denial and the lengths to which it went to refuse responsibility.

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“There’s an analogy we draw in the book to Big Tobacco,” he told Discovery News. “I think it’s apt in the sense of looking at [the league] as a big corporate entity trying to protect itself.”

But the concussion issue is only the tip of the iceberg. Despite America's love for the game, the NFL as an organization is riddled with problems -- including domestic abuse -- that make the league, well, not so super. So feel free to play referee as you click through the following slides. Get ready to throw your flag, for there are many penalties ahead.

Research shows that the brains of former NFL players are abnormal due to serious trauma. Ann McKee, VA Boston, Boston University School of Medicine

At the heart of the concussion controversy is chronic traumatic encephalopathy (CTE), a degenerative brain disease found in individuals with a history of concussions and other head injuries. Symptoms of the disease include memory loss, dementia, aggression and depression -- signs that many former NFL players are starting to experience. Players that have been diagnosed with the disease are dead, because CTE can only be confirmed posthumously.

Despite numerous independent studies and doctors who’ve raised red flags linking CTE to concussions sustained while playing football, the league still maintains its innocence. Twenty years ago, the league said the concussion controversy was a media-created problem and not a real issue for the NFL. Though former NFL Commissioner Paul Tagliabue created the Mild Traumatic Brain Injury Committee in 1994 to publish investigations on the matter, the group was composed of league-affiliated doctors and researchers.

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“The papers themselves were published in a journal that was basically co-opted by the league and edited by a consultant to the New York Giants,” Fainaru-Wada said. “It published paper after paper suggesting there are no real issues around concussions.”

While the league recently agreed to pay $765 million to settle a lawsuit brought by 4,5000 players and their families who accused the league of deliberately covering up knowledge about the consequences of repeated head trauma, details of the agreement state that the payout is not an admission of guilt by the NFL.

“When you still have the Commissioner [Roger Goodell] stating publicly that he’s going to let the doctors decide whether there’s a connection become playing football and brain damage, I think that’s surprising to a lot of doctors who’ve been studying this issue for as long as they have,” Fainaru-Wada said.

NFL legend Junior Seau died on May 2, 2012, from an apparent suicide at his home in San Diego. Louis Lopez/ZUMA Press/Corbis

Former player Dave Duerson was found dead in 2011 from a self-inflicted gun wound to the chest. Prior to pulling the trigger, he texted his wife and left the following note: “Please, see that my brain is given to the NFL’s brain bank.” Neurologists at Boston University later confirmed that Duerson did suffer from CTE.

Former player Junior Seau also committed suicide the same way, gunshot to the chest. Seau’s family was contacted by two of the foremost authorities on CTE, yet the NFL intervened to steer Seau’s brain to the National Institutes of Health (NIH), four months before the NFL gave the institution a $30 million donation.

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Forensic pathologist Bennett Omalu was originally tasked to perform Seau’s autopsy, yet mid-procedure, Seau’s son called and halted the operation. He said NFL had convinced him Omalu’s research and ethics were bad.

Not surprisingly, the NFL had motives for the snub. In 2005, Omalu was the first researcher to diagnose brain damage in a former NFL player, but when he published his findings, the NFL went on the attack, arguing he was wrong.

“The league essentially kept the brain from going to the two neuropathologists who had done more studies on the brains of NFL players than anybody,” said Fainaru-Wada. “I think that raises questions.”

More recently, ex-player Paul Oliver was found dead with a self-inflicted gunshot wound. In the last nine years, 11 former NFL players have committed suicide.

Kyle Turley performs during Day 2 of the Voodoo Experience at City Park in New Orleans, Louisiana on Oct. 29, 2011.Amy Harris/Corbis

To receive full benefits, an NFL player must play four years to be certified as a “vested” player. However, the average career of a player is three-and-a-half years.

Kyle Turley, one of the former players included in the recent lawsuit settlement, believes the NFL has provided inadequate disability benefits and pensions. He’s even seen some ex-players with kids end up homeless, living in cars. “Even players who are supposed to receive those benefits are having a lot of trouble with the system, which was notoriously set up to deny claims,” he told Sports Illustrated.

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A vocal critic of the NFL, Turley founded music label Gridiron Records in 2006. Despite being wracked with injuries and post-concussion syndrome, Turley tours the country fronting his own country band and raising awareness and money for the Gridiron Greats Assistance Fund, a nonprofit organization that provides financial support and free medical assistance to retired NFL players.

“The majority of former players don’t receive benefits, and I don’t know a single person who walked away from professional football without vested status who didn’t have some sort of serious injury,” he added. “Those injuries will bother them, and be a great hindrance to them and their families.”

Vince Young was Young was drafted by the Tennessee Titans in 2006 and spent the first five seasons of his career with them. Greg McWilliams/Icon SMI/Corbis

In 2009, Sports Illustrated estimated that 78 percent of former NFL players are bankrupt or undergo serious financial distress within two years of retiring. While Lawrence Taylor, Terrell Owens, Vince Young and Michael Vick are just a fraction of the more notable names to file for Chapter 11.

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Numerous factors contribute such financial ruin: players living outside of their means, poor investment choices, supporting family members and entourages, substance abuse, gambling and/or sex addictions, domestic violence and divorce.

Though the NFL holds workshops to educate rookies on such matters, many young high-paid players have a hard time envisioning, much less planning for, life after football. Combine that with the consequences of unforeseen brain damage and a league with a bad reputation for taking care of former players, and you have the perfect storm for financial crisis.

Aaron Hernandez, former player for the NFL's New England Patriots, attends a pre-trial hearing in connection with the death of semi-pro football player Odin Lloyd.DOMINICK REUTER/Reuters/Corbis

When former Patriots tight end Aaron Hernandez was charged with first degree murder, the incident led to another round of critics speculating whether the NFL had a crime problem.

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While the nearly 700 player arrests since January 2000 may sound like a lot, according to one study, arrests are actually on the decline since 2006. Part of the perception that the NFL is riddled with criminals is due to the immediate media splash that high-profile athletes make when arrested.

Still, when framed in the context of the NFL, crimes such as former Chiefs linebacker Jovan Belcher’s murder-suicide in 2012 and Cowboys defensive tackle Josh Brent’s recent intoxication manslaughter conviction can easily overshadow the statistics.

Cheerleaders routinely make between $70 and $100 per game.DAVID RYDER/Reuters/Corbis

NFL players may get paid tens to hundreds of thousands of dollars per game, but cheerleaders routinely make between $70 and $100 per game. While some cheerleaders may get a monthly salary between $1,000 and $1,500, such small change makes it nearly impossible to make a living.

Though charging appearance fees at public and private events and hawking titillating calendars can net extra income, cheerleaders often have to adhere to strict weight and beauty regimes not covered by the league or teams.

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While sexual objectification and low pay would quickly turn off most women, many cheerleaders say the job is more of a seasonal, part-time hobby full of game-day camaraderie. Others, like Raiderette “Lacy T.” aren’t so cheerful. The 27-year-old woman is suing the Oakland Raiders for allegedly paying their cheerleaders less than $5 an hour.

Interested in taking a peek a Baltimore Ravens cheerleader contract from the 2009 season? Have at it, thanks to a former cheerleader who handed a copy over to Deadspin.

Even though human growth hormone is a banned substance, the NFL has no formal system in place for testing. KEITH BEDFORD/Reuters/Corbis

Due to disagreements between the NFL and the NFL Players Association on key elements of a performance enhancing drug policy, the league currently has no testing program for human growth hormone (HGH), a banned substance.

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The standoff focuses on how the appeals process would function for players who perhaps didn’t test positive for the banned substance, but were implicated in HGH-arrests or scandals like the Biogenesis clinic crisis that rocked Major League Baseball and exposed high-profile players such as Alex Rodriguez.

NFL Commissioner Roger Goodell wants to possess authority over these appeals while players want an independent arbitrator. With both sides in gridlock, even Congress has threatened to step in. Last September, Rep. Elijah Cumming, ranking Democrat on the House Oversight and Government Reform Committee, publicly scolded the NFLPA and threatened government intervention.

Public tax money subsidizes the NFL, including commissioner Roger Goodell's huge salary.ERIC THAYER/Reuters/Corb

Although the NFL rakes in nearly $10 billion a year, inflating the bank accounts of millionaire players, billionaire owners, television networks and corporate sponsors, the NFL headquarters is actually treated as a non-profit organization.

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Thanks to small tweaks to the original charter legislation 50 years ago, the league enjoys tax exempt status and receives taxpayer-funded subsidies, all while commissioner Roger Goodell collects a $30 million paycheck every year.

Harvard researcher Judith Grant Long calculated that 70 percent of NFL stadiums have been built with taxpayer money. “In general, the public subsidizes pro football to the tune of around $1 billion a year,” Gregg Easterbrook, author of “The King of Sports: Football’s Impact on America,” told NPR.