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NFL football is played by two sets of rules.

There are the official playing rules and casebook, available for anyone to freely read at NFL.com; the guidelines on everything from air pressure to zebras are contained within. The scoring rules, penalties and accepted interpretations thereof fill 120 electronic pages.

Then, there are the rules that aren't written in any book. They aren't downloadable from a website or watchable via any streaming app. Sometimes, ex-players talk about them on TV when one is broken—but fans are never really sure what they are, how many they don't know about or if they're even real.

On the field, in the locker room, even on the team plane, NFL culture is all-encompassing. The only way to get along is to live by the rules, and that's why veterans take it upon themselves to teach every rookie class what you do, and what you don't do, in the NFL. Sometimes, though, the only way to learn the rules is to break them.

Bleacher Report talked to active and former NFL players to figure out where the unspoken lines are drawn, how they're delineated for newcomers and what happens to those who cross them.

It Ain't What It Used to Be

Several players made sure to point out the sport has changed a lot in recent years.

Cellphones are everywhere, players are managed more like movie stars than football players, and the Internet-driven news cycle never stops. Practices are lighter, shorter, less frequent and far less often padded. Training camps are mostly held at team facilities rather than far-off college campuses, and every NFL game is monitored by a forest of high-definition cameras.

Now, more than ever, the NFL culture is public. Many old secrets aren't so secret. A lot of the unwritten rules have been put into words and enforced by the league. There isn't much room for out-and-out thuggery or eye-for-an-eye policing of it. Older fans might say important parts of football culture have been lost.

Former All-Pro guard Steve Hutchinson, a breath after disparaging the work ethic of today's players to Bleacher Report, laughed and admitted complaints about the changing facts of football life have been going on since long before his time.

"This is an ongoing debate," he said. "You talk to guys from the '60s, and they'll say, 'You know, when I played, I walked uphill both ways in the snow!'" But there are still plenty of must-follow rules fans and media never hear about. Most of them deal with the day-to-day reality of playing football for a living: games, practices, meetings and travel.

Every rookie eventually gets with the program—or gets out of the NFL.

First, Do No Harm—At Least Not On Purpose

Every player Bleacher Report talked to agreed on this point: The No. 1 rule, whether it's practices or games, teammates or opponents, is to not purposely injure another player.

"This is our work," Cincinnati Bengals tackle Eric Winston told Bleacher Report. "This is how we feed our families. We're compensated very well for it, but if you try to take that away from someone?" Winston, like many other players, stressed that hard, clean hits are part of the game—and injuries happen. But using dangerous techniques or going after defenseless players is beyond the pale.

"Those shots where players blatantly go after guys in a way that could really hurt someone, after the play, after the whistle? Even the most hardened guys that are considered the real tough guys in the league are like, 'You don't do that.' It's a fine line, but there's a way to be the toughest guy out here—the strongest, most physical—that's not like, 'I'm blatantly trying to hurt somebody.' It's hard to describe, but it's there—and everybody knows it's there."

Crack-back blocks, peel-back blocks and many other such techniques that target the knees or head have been banned by the league office. Hutchinson cited Warren Sapp's 2002 leveling of Chad Clifton as the kind of line-crossing stunt that used to get policed on the field but now gets policed by Roger Goodell.

"The head coach of Green Bay, [Mike] Sherman," Hutchinson said, "ran out onto the field and got in Sapp's face. I mean, you just don't do that. Was it illegal at the time? No. Is it illegal now? Yes." Were a player to do what Sapp did in 2002 today, Hutchinson said, "I'm sure he'd get a letter with a pretty hefty fine in it on Wednesday."

Rookies Should be Seen, Not Heard

"Rookies that think they know what they're talking about make me roll my eyes harder than anything else," said Winston. "Guys that are like, 'Oh, that team's probably easy.' You have no idea until you've done it." Winston, currently president of the NFL Players Association, has guided eight different classes of rookies through training camps with four different teams.

John Minchillo/Associated Press/Associated Press

"No matter who you were or what you were before you came to the NFL," said Winston, "you've got to go back to the beginning." Several players, including Winston, compared being a rookie to being a college freshman.

"You came from a place where you were the big man on campus," Winston said. "Everybody who comes into the NFL, even if you were a sixth-round pick, you were still probably one of the best, if not the best, players on your team." Players who keep their heads down and work will always earn the respect of the veterans more quickly than those who come into the league thinking they know everything.

"When I was a rookie," Hutchinson said, "I didn't say anything to anybody. You know, I started every offensive snap my rookie year for the Seahawks. But in practice, I didn't let anyone older than me hold the bag in individual drills. I didn't care if I was a first-round rookie and he was a third-year practice-squad guy. He was older than me." This kind of deference is exactly what vets love to see, especially from a top pick.

"The guys who've been around for a while," said Winston, "want to see the new guys come in and say, 'OK, I'm going to help you however I can' and not try to do anything else but that." Rookies with big mouths—especially when they don't help the team win games—are in for some very rough practices. The phrase "take care of itself" was used by multiple players.

JIM BRYANT/Associated Press

"I mean, you got a cocky rookie," Hutchinson said, "they're either going to show up and play—in which case, they aren't going to be treated like a rookie anymore—or if he's a bust or he doesn't perform, that'll take care of itself, if you know what I mean. The NFL has a pretty unique way of weeding itself out."

"The ones who don't get it," said Winston, "after they do it for a year, they're like, 'Holy cow.' I think they have so much more respect [for veterans] once they realize how idiotic they sounded."

"Veterans don't like rookies," Matt Bowen told Bleacher Report, "and we all know why." Bowen, a former NFL safety who currently works as a Bleacher Report NFL Lead Writer, put it succinctly: "It's because rookies are drafted to replace veterans."

Ultimately, the rookies are there to take the veterans' jobs. The least the rooks can do is be humble about it.

Seniority Rules

"Seniority rules pretty much everything," Hutchinson said. "In the training room, if there's a line of guys to get taped and a 10-year vet walks in, well, he's going to trump everyone else waiting. Rookies were told to get in early. Training-camp practice starts at 8:30. They needed to be in there by 7, 7:15 if they wanted to get taped."

Though seniority is applied whenever there's a line or a wait for anything—tape, food, medical treatment—it might be most strongly enforced when traveling.

"Coming back from an away game," said Chris Simms, a former NFL quarterback who now works as an NFL Analyst for Bleacher Report, "really only the veterans are going to sit at the front of the bus because they want to be able to get out quickly and get to their cars. They're afforded that privilege." In some cases, Simms said, all the top veterans get to sit on Bus 1 with the coaches, while rookies are relegated to Bus 3 and Bus 4.

SCOTT AUDETTE/Associated Press/Associated Press

Nearly all the players said seniority is strictly enforced on team flights.

"The vets get to pick their seat, the rookies get what's left over," Bowen said. "I don't care if that's in the bathroom. If that's what's left, that's where you're sitting."

"Everybody sits in coach," Hutchinson said, "and the coaches sit in first class. That being said, the older vets have exit-row priority. I know [then-head coach Brad] Childress had a rule when we traveled in Minnesota: A guy over a certain number of vested years would get his own row. He might then sit sideways and stretch out." Hutchinson reported, though, he'd heard of at least one team whose vets got even more privilege.

"The Chiefs, when [Dick] Vermeil was there," Hutchinson said. "The older vets would sit in first class, and the coaches would sit in coach." Hutchinson had never seen or heard of that before hearing that's how those Chiefs flew. But in Washington, Bowen said, then-head coach Steve Spurrier let vets with five or more years of service fly first class. Ten-year veteran wideout Donte Stallworth, who worked as a coaching intern with the Baltimore Ravens, said head coach John Harbaugh let legends such as Ed Reed and Ray Lewis sit up front.

Here's one of the gray areas of unwritten rules: Coaches are free to interpret universal truths like "seniority rules" as they see fit—but there are lines even coaches don't cross without consequence.

Coaches Are Treated with Deference and Respect, Not Worship

In college, head coaches rule with an iron fist. They have total control over players' lives, from where they sleep to what they eat. Football is woven into every minute of their waking lives, and everything the coach says goes.

In the NFL, players are grown men. They have lives, families, hobbies, and sometimes charities or side businesses they take very seriously. Older, established vets have often outlasted at least one head coach, if not more—and the oldest vets are sometimes older than the position coaches they take marching orders from.

"The vets have a healthy respect for the coaches," Winston said, "and the coaches have a healthy respect for them. We're all on a team together, in many ways. They're only going to be regarded as well as we play, and we know that we need them to get better."

ROGELIO V. SOLIS/Associated Press

"In college," Stallworth said, "it's a student-teacher relationship. In the NFL, it's more like man to man. When I was young, we used to have to ask the coach if we could go to the bathroom. In the NFL, it's like, 'Dude, just get up and go to the bathroom.' You don't have to ask."

"Offensive line is a different animal," Hutchinson said, "but in the offensive line room, most of the young guys were 'yes sir,' 'yes coach,' 'yes sir,' and then the older guys were, like, cracking on the offensive line coach and on a first-name basis with him."

Both Winston and Bowen said one of the biggest culture shocks for rookies is hearing players call coaches by their first names.

"At some point," Hutchinson said, "If you make it to eight, 10, 12 years, 15 years in the league, you know what you're doing. For me, at the end, and [Vikings offensive line coach] Jeff Davidson will tell you, I mean, there's no point in him correcting me, because I know before the words came out of his mouth what I did wrong."

At the peak of a player's craft, there's nothing a coach can tell him he doesn't already know. At that point, Hutchinson said, the coach's job is to get the young players in the room to strive for that level of work ethic, dedication and technique. The veteran's job is no longer to obediently listen to everything the coach says, but show teammates that even at his level, he's still working to improve himself.

It shouldn't be a surprise that established veterans take a dim view of new coaches who try to change a team's established culture or impose new unwritten rules—especially when they conflict with the old ones.

GREGORY E. SMITH/Associated Press

Tom Coughlin, before he won two Super Bowls with the New York Giants, famously used to enforce a laundry list of rules, written and unwritten, that rubbed a lot of veterans the wrong way. Former Pro Bowl quarterback Steve Beuerlein told Bleacher Report about one in particular.

"There was a line he painted on the edge of the practice field he called 'The Concentration Line,'" Beuerlein said. Players were supposed to drop everything on their minds besides football before crossing that line to practice. "Honestly," Beuerlein said, "I thought it was a bit high schoolish."

Halfway through his 14-year career at that point, Beuerlein and other grown professionals didn't need to be scolded for having non-football thoughts. Beuerlein was quick to credit Coughlin for achieving so much in New York after famously softening his approach.

Stallworth bristled when the subject of former Tampa Bay Buccaneers head coach Greg Schiano's controversial blitzing of victory formations was brought up.

"I am no fan of college coaches coming into the NFL," Stallworth said, "because they do s--t like that. That can get someone hurt." Just about everyone involved in the NFL at the time seemed to recognize the Bucs had broken an unwritten rule, Stallworth said—except Schiano and his defenders.

Like any man-to-man relationship, when things go bad, tempers can flare. With coaches relying on players to make them look good and players relying on coaches to put them in position to win, everyone's career rides on one another—and when the stakes are that high, almost anything can happen.

"I've seen coaches go after players on the sideline," Bowen said. "I've seen coaches have to be pulled back from players and players have to be pulled off of coaches."

Don't Talk About Your Teammates' Contracts

The NFL is a job. As in any professional workplace, who makes what salary can sour workplace relationships and be a matter of intense jealousy. Unlike most workplaces, what every employee in the locker room makes is known, to the dollar, by everyone else in the room—and everyone else in the world.

That's why they don't talk about it, according to Stallworth.

"I actually learned that a very long time ago, from Michael Irvin," he said. "He told me before I had played a down. I didn't know any better, but Joe Horn—and remember I was drafted in the first round, 13th pick—but Joe Horn was obviously the man there, and he was going to continue to be the man. But he was holding out, trying to get a new contract.

"I didn't even know this at the time. I wasn't yet that immersed in what was going on in the world or even really the NFL, for that matter. I forget where I ran into Michael Irvin, but it was before the season started. He said, 'One thing that you never want to do is mention another player's contract. It's one of the rules. It's an unwritten rule, but you don't mention that.' I had no idea what he was talking about! I was just like, 'Oh, that's a good piece of information.'

"Once I got to New Orleans, I had my first meeting with the media, and, of course, they were asking about that. That's when it popped back into my head, like, 'Oh, s--t! This is what he meant!'

"It's good because, in the end, every man is in his own situation. You shouldn't say anything about anyone's contract, because everyone has their own situation with the team. I told the media, 'That's Joe's contract, and he's a great player, and I can't wait for him to get in here and learn from him.'

"I understood in that moment what Irvin was talking about."

If a Vet Says, 'Jump'

Rookie hazing has been disappearing from the NFL in recent decades. While many harmless traditions, such as being forced to sing your college fight song, continue, cruel and dangerous tricks have either been explicitly banned by coaches or rendered moot by more effective ways to acclimatize young athletes.

"A lot of it is just veterans showing you around," Super Bowl-winning quarterback Brad Johnson told Bleacher Report. "Little things, like you have to learn you've got to tip the equipment guy. There's a process for taking care of in-house people, from equipment guys to trainers." Veterans teach rookies to respect the staff serving them, but they also demand respect—and service—from the rookies.

"Rookies buy breakfast," Bowen said. "That could be doughnuts, biscuits or Egg McMuffins, but as a rookie, you have to understand that that's your job. You're not supposed to complain about it. You're just supposed to understand: 'I'm a rookie. On Fridays I bring breakfast.' Whatever the veterans want. Now, if you have good veterans, they're not going to kill you over it—and I'm talking about price. You're talking about Dunkin' Donuts, Krispy Kreme, McDonald's, Burger King."

"Usually," Johnson said about rookies buying breakfast, "if you're the first-round pick, you got the first week. Then second round, third round. It goes in order."

EVAN VUCCI/Associated Press

"You have to understand as a rookie," Bowen said, "that when the veterans are done with practice during training camp, they're going to leave their helmets and shoulder pads there, and it's your job to pick 'em up and carry 'em." This, Bowen said, sometimes leads to complaints about disrespect.

"That's not disrespect at all," he said. "Earn your stripes. You're a rookie. You carry the pads into the locker room. After this year, you can do whatever you want. You can make the next year's class carry your pads into the locker room." Bowen shared a story about his own personal league initiation.

"When I was a rookie in St. Louis," he said, "there was a veteran defensive lineman who told me I had to get coffee for him every morning. He didn't like the coffee in the dorms. So I had to find a way to get him coffee.

"Now, I didn't have a car—I was a rookie sixth-round pick. So I had to borrow a bike every morning, get up half an hour early, bike to this convenience store the veteran liked the coffee from, get the coffee, try not to spill the coffee on the bike and have it in his locker at 6 a.m. If I didn't, well, I did it every time because I was afraid to know what would happen.

"Some people might call that 'hazing.' Is it hazing? I don't know. I just understood that I was a rookie and this is part of my initiation. A veteran tells me to do something, I do it. If a veteran says, 'Jump,' I ask, 'How high?'"

"I, for one," said Simms, "during away games, always had to carry Warren Sapp's bags to his room. I was also expected to have a can of Skoal on me at all times. It was just part of my indoctrination into the football team."

Then, there's the matter of rookie dinners.

It's well known that veterans will take a rookie or all the rookies who made the team out to dinner and run up a massive tab. In recent years, the dollar figures have become astronomical. As the most outrageous begin to creep closer to six figures rather than five, some NFL vets are starting to speak up against the most punitive bills.

That said, most of the players Bleacher Report talked to agreed: That bill goes up when a rookie is drafted especially high, is especially cocky, fails to live up to his draft status on the practice field or any combination of the above.

In 2010, per Tim McMahon of ESPN.com, Dez Bryant refused to carry veteran receiver Roy Williams' pads during training camp. Per ESPN.com's Calvin Watkins, Roy and the rest of the Cowboys offense later enjoyed a $54,896 meal at Pappas Bros. Steakhouse—all at Bryant's expense.

Learn to Practice the Professional Way

One of the most common complaints of NFL veterans is that rookies don't know how to practice.

The NFL year, with its training camp, preseason, 16-week regular season and playoffs, is a much, much longer grind than the college season—and there are no patsies.

"There's no East Carolina State [on the schedule]," Winston said. "There's 16 Florida States, 16 University of Floridas," the University of Miami product added. Practicing in the NFL is a tricky balance of executing at a high level but doing so in a controlled, measured, sustainable way.

Stephan Savoia/Associated Press/Associated Press

"The rookies are used to practicing 100 miles an hour throughout the season," Stallworth said, "even when doing drills that aren't really meant to go 100 miles an hour. You'll hear it every year. One of the veterans will say, 'Damn, man, we need to teach these rookies how to practice!'" Stallworth said it's not that practices aren't ever all-out, but there are times when you put it all on the line and times you don't.

"That's the hardest thing for rookies, learning how to practice," Bowen agreed. "Rookies play out of control. They always do during training camp. They're excited. Their heart rate is up. They wanna make a play. Then, they get tired. They're always going on the ground, getting in the veterans' way, or they run into the quarterback or do something stupid." Bowen said staying off the ground is a key unwritten rule.

"There's nothing a veteran hates more," Bowen said, "than being in position to get injured because a rookie can't stay off the damn ground. Vets will let you know about it and let you know about it quickly. Practice fast, practice physical, but do not put the veterans in jeopardy."

"If you're on the Dallas Cowboys," Bowen said, "working on the scout team, and Dez Bryant comes across the middle, you're not allowed to lay him out. If you do, you're gonna get cut." This is not an idle threat, Bowen warned.

"When I was in Green Bay," he said, "they told me, 'If you hit Brett Favre in practice, we'll give you an apple and a road map out of town.' I saw it happen. I saw a defensive lineman hit Favre in practice. He was not there the next day. He was gone."

Consequences

Breaking the unwritten rules, as Bowen's short-term teammate did, has real consequences—whether enforced by the league, team or teammates.

"The last thing you want as a rookie," Bowen said, "is to get in a situation where the veterans don't accept you, because, one, they're going to come after you in practice. Back then, we had two-a-days, and we were in pads every day; it was a lot more physical. Certain things were done in practice then that would never happen today in terms of the amount of hitting and live contact. It was full go every day.

"We had to put on a rookie show in a bar down in Macomb [Illinois]. We had to put on skits, provide all the entertainment, do all that. ... If you didn't want to do it, that would be a really bad idea. A really bad idea. Especially with a veteran team like that—this was 2000, they were just coming off a Super Bowl win—you have Hall of Fame talent there, guys that have been playing for 10-plus years. If they tell you to do something, you'd better do it—or you'd better strap on your pads pretty tight at the next practice."

Johnson told Bleacher Report that long ago, before he played, rookie hazing would get "a little out of control" and that coaches had to step in to "make sure it's all in good fun."

He shared one elaborate but harmless way to not only punish rookies greedy for the perks of being a famous athlete but also teach them a lesson about loose lips.

"At Thanksgiving, you're supposed to give back, right?" Johnson asked. "Well, what we would do in Minnesota was, we'd have a letter. And the coaches would stand up and say, 'Anyone who wants their free turkeys can go down to the local store, talk to the butcher and give the butcher this letter,' and they'd give them their turkey for free.

"So you've got these guys, the rookies, who instead of giving back are thinking they're getting free turkeys. Well, the thing was there'd be a hidden camera. And the local newspaper and TV people would be in on it.

"And then the butcher would ask, 'Who are you? What position do you play? Do you like your coach? Is your quarterback any good?' Just kind of antagonize them a little bit, see if they say anything that probably shouldn't be said. And then the butcher would point out the letter was signed by a guy named 'U. R. Turkey,' like, you're the turkey."

Hutchinson said that back when he was drafted by the Seattle Seahawks, players who said disrespectful, clueless or just plain stupid things were also in line for a meaty gag gift.

"The captains and trainers had this thing they called 'The Run for the Tongue,'" he said. "Anytime anybody said anything like, 'I can't believe this guy just said that,' and there was a witness to it, it got written in a notebook.

"So near the end of the season, the last couple weeks, they wrote all the quotes and the guys who said them on the big grease board in the training room—in the form of, like, NCAA brackets, like they were seeded.

"So then the captains and trainers voted on each round. The winner would get a gift certificate to the Metropolitan Grill, the famous steakhouse in Seattle, and they got a cow tongue. That's why it was 'The Run for the Tongue.'"

Hutchinson said that in today's social media-saturated locker room, some of the hare-brained quotes would probably be made public one way or another. As it is, some of the can't-believe-it quotes live on in Seahawks lore.

"There was a player," Hutchinson said. "Truthfully, I don't remember who. I think it might have been the year before I got there. This was when Seattle was still in the AFC West. But there was a player, he was a rookie, and he got off the bus in Denver to play the Broncos.

"He gets off the bus, looks up at the stadium, and goes, 'Man, there ain't no way that motherf----r's a mile high.' Everybody just looked at him.

"He literally thought the stadium was going to be a mile high."

Johnson relayed the tale of two young Minnesota Vikings who'd gotten out of line. Their street clothes were taken, wetted down and then draped over the goalposts. In winter. In Minnesota.

As with Bowen, Simms saw what happened when a rookie refused to listen to a perennial Pro Bowler on a Super Bowl-winning team loaded with perennial Pro Bowlers.

"It's my second or third year in the NFL [it was his second], and we get a young offensive lineman named Jeb Terry," he said. "Of course, we have Mike Alstott at running back, and we're in the locker room, and Alstott decides he wants a Gatorade. So he goes, 'Hey, rook. Hey, Jeb. Get me a Gatorade.'

"Now, all the kid had to do was basically walk across the locker room to the refrigerator and get him a Gatorade. Well, he says, 'No.' Everybody was like, 'Ohhhhhh!' You know? Like, 'Ohhhhhh. Whooooooa. He said no!' Alstott just kinda looks at him, smiles and shakes his head. Of course, I'd been there [a couple of years], so I knew he was going to get it.

"So the next day, what happens? We walk into the locker loom, and the hood of his truck is at his locker. His four wheels are hanging from the goalposts, and his truck is sitting in the parking lot on cinder blocks."

Acceptance

When do young players finally stop being taught lessons? When do veterans finally accept the young players know the rules?

The rookie-specific traditions such as buying breakfast end when the players stop being literal rookies. Toward the end of that first season, though, players either begin climbing up the totem pole with their play on the field or don't.

Seth Wenig/Associated Press

"Most veterans are not going to accept a rookie as part of the team," said Simms, "until he contributes to that team winning games. That's one of the unwritten rules most people don't realize. The first time I stuck my hand out to Warren Sapp, he goes, 'Don't even talk to me until you've played in a game here.'"

Simms wasn't taken aback by this. "I understood," he said. "They didn't need me; they'd just won a Super Bowl."

Especially on a veteran team with high expectations and always with the first-round picks, players want to see rookies perform. If they're going to be there and get paid, they have to be contributing. Rookies who make huge, instant impacts (see: Beckham Jr., Odell) stop being treated like rookies at all.

Appendix

This is hardly an exhaustive recounting of all the unwritten rules of the NFL. In fact, the surface has barely been scratched.

For many of the players Bleacher Report talked to, it was difficult to describe football culture to outsiders because they've never really lived outside of it. Others weren't comfortable sharing the inner workings of the teams they played on—or were so overwhelmed by the amount of material they couldn't narrow it down.

"I could write a book," said Hutchinson, and he certainly could. But no matter how many stories are shared or how many fines are imposed, football will always run on a set of unwritten rules.

These gladiators' livelihoods will always be sacrosanct. The sacrifice and effort of the elders will always be honored, and the selfish and short-sighted will always be humbled. The rules of engagement might be written down somewhere, but truly exist in the space between two colliding men.

No matter how much technology, fan interest and well-intentioned legalese invades every nook and cranny of the NFL, players will still need a set of guidelines for coping with the reality of life in pro football.

There will always be a right way to play the game—and the only way to learn it is to live it.