(CNN) Super Bowl Sunday is a religion of sorts for millions of Americans who gather to watch the NFL's greatest showcase.

And there's no question in George Atallah's mind that this year's game between the Atlanta Falcons and the New England Patriots is a clean one.

Atallah is director of external affairs for the NFL Players Association (NFLPA) , the pro football players' union. The NFL and the NFLPA work together under their collective bargaining agreement to determine the league's drug-testing policy.

Players "want to know that the guy across from them is not cheating," Atallah said. When asked whether the league and the union are doing everything they possibly can to catch cheaters, he said the NFLPA is "proud of (its) drug policies."

According to Sportrac , a site dedicated to tracking NFL player suspensions, 19 of the league's more than 1,600 players were suspended this past season for violating the NFL's performance-enhancing drug (PED) policy. That number is based solely on news reports, because the league and the players' association don't release that information publicly.

Former players have said PEDs, which can include human growth hormone, testosterone and even the ADHD drug Adderall, are rampant. But Atallah doesn't profess to know the degree to which NFL players are taking such drugs.

"I don't know the answer," he said. "Only the players in the locker room know."

The 'gold standard' of drug testing

When it comes to testing for PEDs, the protocols of the United States Anti-Doping Agency and its international counterpart, the World Anti-Doping Agency, have been called the "gold standard" of testing. The Us agency was created to oversee the US Olympic team and tests athletes for the Ultimate Fighting Championship , the professional mixed martial arts league.

In fact, UFC is the only professional league in the country to turn its testing over to the USADA. Major League Baseball, the NFL and others craft their testing policies as part of the collective bargaining process between the players' union and the league. And some critics say that relationship can result in putting the leagues' interest ahead of the players.

WADA began keeping and updating a list of prohibitive PEDs in 1999. To be labeled a PED, it must meet two of three criteria: It has the potential to enhance sport performance, it represents an actual or potential health risk, or it violates the "spirit of the sport."

Urijah Faber stands on the scale during the weigh-in for a UFC tournament last year.

To keep its athletes safe, the UFC wanted to have them tested under the most stringent standards. By the USADA's protocols, that means in and out of competition periods, 365 days a year.

Under USADA policy, a UFC athlete can be asked to take a drug test anywhere, anytime -- at home, at practice, even at school. Once the doping control officer has made the notification, he or she will stay with the athlete until the sample has been provided. That means the officer will watch the athlete's every move, including following them into the bathroom for the sample.

"This is the first time you guys are not waking me up at six in the morning," UFC athlete Urijah Faber , 37, told USADA doping control officer Gary Robbins after Robbins surprised Faber at his gym in Sacramento, California.

Faber, a 13-year veteran of the UFC, has been tested by the USADA 12 times. The USADA has been independently handling all UFC drug testing since 2015, including for PEDs. The UFC is deliberately hands-off.

Jeff Novitzky, vice president of athlete health and performance for the UFC, in 2016.

"We are required to keep our whereabouts known at all times," said Faber. "It I wanted to jump on a plane and go to Mexico today, I'd have to let everybody know. I can still go. There (are) no requirements as far as where I'm gonna be ... if they want to track me down and hang out in Acapulco or whatever."

All UFC athletes -- more than 530, spread across nearly 40 countries -- must comply with the athletes' 24/7 whereabouts program, which can be updated and monitored through a phone app. If a doping control officer arrives and the athlete is not at the location provided on their whereabouts, the USADA will wait 60 minutes. If a second location is provided, they will arrive there and wait another 60 minutes. If they are unable to make contact, they will call the athlete and inform them they have 60 minutes to report for testing. The doping control officer may make arrangements to meet the athlete at another location.

The USADA says that for the most part, UFC athletes have been very good about complying with its policies. It hasn't had to issue any sanctions for whereabouts failure, though there have been numerous instances of this occurring with Olympic athletes, according to the agency.

An agent for change

It was former US federal agent Jeff Novitzky, now vice president of athlete health and performance for the UFC, who was hugely instrumental in bringing the two organizations together a year and a half ago.

Novitzky got involved in the world of anti-doping in 2002 and made a name for himself for the investigation he conducted on BALCO Laboratories. It involved several dozen high-profile athletes, including baseball stars Barry Bonds and Jason Giambi and Olympian Marion Jones, who were clients of BALCO.

Novtizky has his own theory on why players dope. "There (is) always a risk-reward calculation. There is clearly a reward for a professional athlete to use these drugs. They make already gifted and great athletes even better. They make them bigger, faster, stronger, and increase endurance. When you couple that with financial incentives in professional sports today, an already great athlete using performance enhancing drugs can be even greater and make even more money than they make," he said.

"On the risk side, most of them are looking at 'how likely is it that I would get caught? How comprehensive is the anti-doping program in my sport, and what kind of sanction would I be facing if I was caught?' If the sanction is small and it's a matter of weeks or months and financially is not too severe, what athletes have told me is that it's worth the risk," said Novitzky.

But Atallah, who's been director of external affairs for the NFLPA since 2009, said he "completely" disagrees. "The average career of an NFL player is just over three years. If you get suspended for a performance-enhancing drug, the penalty (for a first-time offender) is four games. In that four games somebody else is fighting to take your job," he said.

"So I disagree with the premise that there's no risk or that the reward is greater than the risk for a professional football player to cheat. You're cutting a significant percentage of your career and potentially life earnings if you get caught doping in the NFL. That's not a small risk."

Novitzky's mission is clear. He says he wants to keep his athletes safe because he's seen the damaging effects of these substances, including death.

"Tragically in my investigations, I saw a couple of instances of young kids who got on these powerful hormonal substances. It affected their physical well -eing and their mental well-being. I've seen liver transplants," he said. "When you take someone who is not knowledgeable ... the results can be very detrimental."

Protecting the hardest-hit athletes

Not only can using PEDs complicate health matters, but in combat and contact sports, they change the level of the playing field.

Faber, now retired from the UFC, knows this firsthand.

"You're trying to mess someone up, so if somebody has something that's illegal, it's like drinking and driving or pulling the trigger on a gun, I would think," he said. "In my opinion, you're changing the weapon and not using the rules, and if somebody's life was taken or some physical damage would happen above and beyond the ordinary, you gotta look at that."

Atallah says that safety is important but that it has to be balanced with the rights of NFL players to be tested.

"It's odd to me that the anti-doping community is so fixated on labeling athletes and treating athletes as if it's a forgone conclusion that they are going to cheat," he said.

"The real issue is what you are doing (in the) anti-doping community to provide athletes with a fair due process, a recourse or a system that gives the athletes the rights to challenge any nefarious positive test."

The UFC maintains that year-round testing makes its sport safer.

"It is, without a doubt, a safer sport," said Faber. "Within training, within a fight situation ... your body is made for certain levels of torque and certain levels of explosiveness and power. So by keeping the joints where they're supposed to be and everything attached, I'm sure that injuries will be lessened."

Faber used to post his drug test results on Twitter. Novitzky encourages other athletes to apply similar positive "peer pressure" to help with buy-in from the public.

Not all PED testing is built alike

It is the UFC's goal for its testing policy to be the best anti-doping program among all professional sports, which is why it's handed the reigns over to the USADA. And that means following the USADA's 365-day testing policy, anytime, just like Olympians.

Other US pro sports leagues -- in which hard impacts are also part of the game -- simply do not adhere to the same level of transparency set by the UFC. Even the protocols themselves are not public.

The NFL, for example, is far less vigorous. Each week during the season, which runs from September to February, the NFLPA randomly selects 10 players per team to be tested for testing. Though specimens may be collected any day of the week, the collection of blood specimens is prohibited on game days, and a player cannot be asked for more than six blood tests per year.

For NFL specimens collected at a training facility or a stadium, players have up to three hours to deliver it from the time they were notified. For specimens collected anywhere else, such as their home, the player has to schedule a time for specimen collection within 24 hours of notification.

In the UFC, the doping control officer keeps an eye on the athlete from notification time to having the specimen in hand -- including watching them in the bathroom as they provide the sample. But not the NFL.

"To suggest that we need to add additional layers of voyeurism to what is already an invasive testing protocol is not necessarily going to make it more effective," said Atallah.

But Novitzky sees holes in these protocols.

"There should never be any limitations, in my experience," he said. "When 10 players have been tested from the team, they know nobody else is going to be tested that week. So that's an issue."

Another hole, he sees, is the time leniency.

"My experience in this world has shown me if you give athletes even a matter of hours of preparing for a test, there (are) things that can be done to manipulate their body to pass a test."

"The amount of blood required for (a PED) test is miniscule, it's literally two tablespoons," explained Novitzky, "which science has shown will be regenerated by the body in a matter of hours. Because of that there's no restrictions on the UFC athlete about when blood can be taken," including before or after a fight.

These differences between the UFC and the NFL amount to "small loopholes that you can drive a semi-tractor through," said Novitzky.

Testing for HGH

Why is having a blood test so crucial? It's the preferred way to measure for human growth hormone, one of the most commonly used PEDs.

"Athletes have told me anecdotally that they can work out super hard late at night and wake up feeling like a teenager the next day," Novitzky said of an advantage HGH offers.

HGH has been around since the 1970s, but 2014 was the first year the NFL began testing for it. The league has yet to uncover a single positive sample. But that may not reflect whether there is abuse.

The NFL uses an isoform test, which detects synthetic HGH. But the test has a very short detection window of just 24 to 48 hours. So if a notification is given to a player to test at home, he may have up to 24 hours before having to submit a sample. The USADA, and in turn the UFC, uses a more precise bio marker test that looks for a chemical fingerprint to detect HGH several weeks after usage.

"I think the (NFLPA) would be open to hearing from the league" about bio marker testing, said Atallah.

The USADA can also create a "biological passport" of an athlete by compiling an athlete's results over time. Such a profile can help identify changes or physiological trends that may occur in an athlete's body. The NFL destroys a player's specimens after 90 days, but the USADA can keep them for 10 years. This allows it to test them again with even more precise technology.

Why pro sports may oppose rigorous testing

The fear of decimating a team may be one reason why other sport leagues are unwilling to adopt the USADA's rigorous model of testing.

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The UFC wants to show other leagues around the world that you can have a gold standard program and still have a successful business model, Novitzky said.

"You're gonna see some bumps and bruises early on. You're gonna see some big-name athletes falling by the wayside. But, eventually, over time, if you do it properly (and) gradually like we did, you'll see similar results as we've seen," he said.

In July, the UFC lost one of the fighters three days before the UFC 200 tournament, where some of its biggest names fought. The USADA called and said it had a positive test for Jon Jones, a former light heavyweight champion, who was pulled from the fight and did not compete.

"I'll tell you, athletes really looked at that and woke up and said, 'Wow, they're not kidding around. It doesn't matter who you are,' " said Novitzky.

But the NFLPA does not sound receptive to the UFC's level of year-round testing.

"We would never agree to a protocol that ... has a GPS-tracking" standard, Atallah said. The NFL has different standards for a what a player does during the season versus off-season, and so it has different testing protocols to reflect that, he said.