Hayes and Long shared a love of jokes, both practical and verbal; hard work on the practice field and in the film and weight rooms; and an intense desire to win on game days. It's a friendship that has had few obstacles, with one notable exception.
Although it can often be hard to tell if Hayes is serious or joking, he vehemently protests that dinosaurs ever walked the earth.
"He thinks archaeologists place bones underground like a parent would place Easter eggs," Long said earlier this season, laughing. "They just planted them. It's some large conspiracy. He does not believe that dinosaurs ever existed and he thinks that mermaids are real. I love dinosaurs, so we have a big point of contention."
It's true. Whether or not it started out as a joke and grew into a conviction is irrelevant at this point. Ask Hayes about the existence of dinosaurs and mermaids and you'll get the type of mythological hot takes you're only likely to find on the furthest reaches of social media and the Internet.
"No, I don't believe dinosaurs existed," Hayes said last month. "Not even a little bit. With these bones, it's crazy because man has never seen a dinosaur, we can agree on that, right? But we know exactly how to put these bones together? I believe there is more of a chance you will find a mermaid than you will a dinosaur because we find different species in the water all the time.
"I don't understand how [Long] just believes in dinosaurs. That's just crazy to me. We know they died. We know what a T-Rex eats? That don't sound crazy to you? We have never seen a dinosaur before but we know exactly where every single rib [was] and which rib goes where. That's crazy to me."
Something that isn't so crazy? Acknowledging that Hayes doubles as one of the NFL's most underrated defensive linemen and genuine characters. In a league filled with clichéd answers, Hayes offers real, unfiltered thoughts on any topic thrown his way. He's the Rams' version of the most interesting man in the world. But beneath the theories and pranks, Hayes is pretty darn good at football and an invaluable piece of the Rams defensive line.
One need look no further than Sunday's 23-17 win against the Seattle Seahawks to see how Hayes can alter a game. He finished with nine tackles, three sacks, four tackles for loss and five quarterback hits in leading the Rams to their first win in Seattle since Jan. 8, 2005.
The numbers were impressive but they don't do much for Hayes, who says he prefers to evaluate his play on how well he handles his responsibilities rather than sack totals.
"I don't really put a lot of effort into, 'Oh, I have got to get these sacks,'" he has said. "My whole thing is I just want to play solid. When it's all said and done, I just want to be able to say at the end of the year I played good football."
More often than not, that has been the case in Hayes' nearly four seasons with the Rams. By his own admission, Hayes' propensity for laughing and joking held him back during his first four seasons in the league with the Tennessee Titans.
When he signed with the Rams after they hired Jeff Fisher, the coach who drafted him in Tennessee, Hayes made it a point to understand there's a time and a place for the laughs and a time and a place when things have to be serious.
For Hayes, the transformation on game days is no laughing matter.
"When Sunday rolls around, it's just all about football," said Hayes, who was so upset by a loss to his former team in 2013 that he cut his arm when he smashed a locker-room mirror. "For me, nothing else is really funny. Even when we are out there at practice in our team periods, I'm in serious mode. But once the offense gets it going, I can sit down and joke around with the guys.
"You have got to know at the end of the day, there's a time and place for play. That's what I had to learn. It took me a long time, until I got to St. Louis, to learn that. My first three or four years in the NFL, I can honestly say it was too much play and I was never serious."
Hayes has posted 153 tackles, 21.5 sacks, three forced fumbles, four fumble recoveries and an interception in almost four full seasons with the Rams. Most of that production has come on limited snaps as Hayes has primarily served as the top backup to Long, though Long's injuries have thrust Hayes into a starting job regularly over the past two seasons.
"He's super important and people don't give him enough credit -- people kind of think he's dopey at times," defensive coordinator Gregg Williams said. "All the goofy things he does and he's always got a smile on his face. He's constantly keeping things stirred up. You guys see him go down and put his head down on the goal post because he's getting ready to go to a dark place when the game [starts]."
Hayes also considers it part of his job to keep Williams on his toes. At Halloween, Hayes showed up to a meeting as what he called a "superhero that believes in saving all mankind." Williams was a bit thrown off his game.
"He quickly has found the fastest way to get my fuse lit," Williams said at the time. "Unless he gets that done every day, he doesn't think he's had a very good day."
Hayes' ability to scheme and execute pranks with Long has become legendary in the Rams' locker room. There was the time he and Long "allegedly" filled linebacker James Laurinaitis' car with 10,000 crickets, a joke so over the top that Laurinaitis had to get rid of the car because many of the crickets died in the vents. Or the times when Hayes and his cohorts hired trailers to pick up teammates' cars and store them on the practice field. Or the time when they moved two cars across the street from the training facility and had makeshift houses built around them.
"I think when it comes to the pranks they do, his mind just goes," defensive tackle Michael Brockers said. "It keeps the mood light, it keeps it fun, it keeps guys wanting to come back."
After the Rams play San Francisco on Sunday, Hayes will join the rest of his teammates and the organization in heading toward an offseason full of uncertainty. He'll be an unrestricted free agent at 30 with gas left in the tank. Although he has had his share of medical procedures in recent years, he still offers value to a team seeking help on the defensive line, especially if he can be kept fresh as part of a rotation.
It would be logical for the Rams to try to bring Hayes back and it would make sense that he'd want to stay, but he could also have his share of suitors. Whoever lands him will get a player who can energize a team on and off the field.
"I try to tell everybody as much as I can about him because I think it would be a shame if the world didn't know," Long said.
Long's message is an important one, for it would be a shame if characters like Hayes were to go extinct.