USA TODAY: A glimpse into the inner world of UFC 158's Nick Diaz

(This story appeared in today’s edition of USA TODAY.)

People say a lot of things about Nick Diaz.

Diaz is a thug and a pothead. Diaz is the last honest and genuine fighter in a world full of made-for-TV phonies. Maybe it’s all true; maybe not.

On a news media call last week, his opponent in UFC 158 (Saturday, 10 p.m. ET, pay-per-view), welterweight champion Georges St-Pierre (23-2 MMA, 17-2 UFC), called Diaz an “uneducated fool.” On the same call, Diaz (26-8 MMA, 7-5 UFC) likened himself to a “superhero coming in with the anti-bulls—.”

UFC President Dana White has never disputed Diaz’s talent as a fighter. But after the UFC welterweight’s first stint with the organization ended in 2006, White wondered aloud whether the scrappy kid from Stockton, Calif., would ever learn to “play the game,” even a little bit.

“You have to follow certain rules and guidelines,” White said in 2010. “The last time Nick Diaz was in the UFC, he got into a fistfight at the hospital with the guy he fought (in UFC 57). You can’t do that kind of stuff.”

But Diaz did. It’s part of his legend, how he started a brawl in a hospital hallway with Joe Riggs, whom he had lost to in three rounds hours earlier.

That’s one of many stories. There’s also the time he threw a shoe at an opponent backstage. Or the time Diaz and his teammates jumped a fellow fighter on live network TV.

The fans who love Diaz can’t get enough of these stories.

The people who are responsible for trying to corral him could stand a little less excitement.

“It used to drive me absolutely crazy,” says Diaz’s manager and longtime trainer, Cesar Gracie. “Like, I couldn’t sleep at night.”

When Diaz would fail to show up for another news conference or video shoot, Gracie’s phone would go off.

When Diaz failed postfight drug tests because of his frequent and unapologetic marijuana use, Gracie had to help put out the fires.

Just getting his client to show up at the airport when the UFC booked him on a flight could seem like an insurmountable challenge.

The last time Diaz was slated to fight for St-Pierre’s title, he blew off one too many news media responsibilities and was pulled from the bout.

This time, a crisis was averted when he skipped Wednesday’s open workouts but managed to make Thursday’s news conference. Still, that constant stress is the kind of thing that drives managers such as Gracie crazy.

“I finally learned that I really don’t have that much control over it,” says Gracie, who began training Diaz when he was a 16-year-old kid who had wandered into one of Gracie’s jiu-jitsu gyms in Lodi, Calif. “With Nick, I don’t think he’s trying to disrespect anybody or be unprofessional. I think he’s just uncomfortable with media and with people trying to delve into his personal life or make him open up. … He hasn’t learned how to relate that way.”

According to those in Diaz’s inner circle, that’s the main difference between the man they know and the character they see portrayed in UFC ads and MMA news stories.

“He gets a bad rap, but he’s one of the most loyal friends I have,” says longtime training partner and fellow UFC welterweight Jake Shields.

To his younger brother, Nate, also a UFC fighter, he’s been part sibling and part father figure, Gracie says.

“If Nick hadn’t been there, things could have been a lot different for Nate,” Gracie says. “There weren’t a lot of opportunities for them to go to school, to college. There were financial issues and family issues. Fighting was really the best thing that could have happened for both of them.”

Diaz is a born fighter. Even his detractors agree on that.

But as training partner and UFC lightweight Gilbert Melendez puts it, “Some of the things that come with being a professional fighter, being an entertainer and doing media and all that, that’s not him.”

Maybe that’s why it seems, at times, as if Diaz despises the sport that pays his bills. It’s not the training that bothers him, his friends all say. He’s known for marathon sessions in the gym and for mixing in the occasional triathlon between fights.

“I think he’s probably the most in shape athlete there is in MMA,” Melendez says. “He’s just a machine, and he’ll outwork you. If every fight were to the death, Nick Diaz would be undefeated.”

But when it comes to dealing with the media, potential sponsors or even his UFC employers, Diaz “doesn’t like getting bossed around,” Shields says. “That’s why he fights. He wants to do what he wants to do.”

Sometimes that results in headaches for those around him; other times it costs Diaz a lot of money and crucial career opportunities. It’s what he brings inside the cage that makes so many people willing to put up with so much outside of it.

If Diaz brings it again Saturday, the fighter who can’t or won’t play the game could leave Montreal as the UFC’s welterweight champion.

Then the game might have to adjust to him.

For more on UFC 158, stay tuned to the UFC Rumors section of the site.