Floyd Mayweather Jr., Marcos Maidana

Floyd Mayweather Jr. (wearing hat) and Marcos Maidana each flash the No. 1 sign after their weigh-in at the MGM Grand Garden Arena on Friday. (Ethan Miller / Getty Images / May 2, 2014)

LAS VEGAS — He's got the hands to crack concrete, but what Marcos Maidana really needs to do is crack the code.

Specifically, the May-Vinci Code.

That's the whimsical nickname Floyd Mayweather Jr. has given the conundrum he's presented for 18 years while baffling the boxing world. Mayweather, who fights Argentina's square-jawed, stone-fisted Maidana tonight, is 45-0 and, even at 37, would be an overwhelming favorite against any welterweight in the sport.

The fight, which will be broadcast on Showtime pay-per-view from the MGM Grand Hotel, is a WBC and WBA welterweight world championship unification bout billed as “The Moment.” Maidana (35-3, 31 knockouts) punched his way into the opportunity with a convincing decision over Adrien Broner in December, twice knocking down his opponent — the only knockdowns of Broner's career — and landing several powerful, chopping overhand rights.

Still, against Mayweather, Maidana is an 11-1 underdog in the main event, which comes after an undercard that features two other compelling welterweight fights: Amir Khan versus Luis Collazo, and Broner versus Carlos Molina.

That is, assuming there is a main event. After Friday's weigh-in, a dispute arose between the fighters' camps regarding the custom-made, horsehair-stuffed gloves Maidana had selected. A fighter's gloves must be approved by his opponent, as well as the Nevada State Athletic Commission.

Both the Mayweather camp and the commission objected to the distribution of padding in the gloves, arguing there was too much weight in the wrist area and not enough padding on the knuckles.

As of Friday night, the situation was unresolved. However, Mayweather's promoter, Richard Schaefer, chief executive of Golden Boy Promotions, all but guaranteed the disagreement would not disrupt the fight as scheduled.

“I am absolutely confident that everything will be worked out,” Schaefer said. “There will be a fight.”

The defense-minded Mayweather has 26 knockouts, but only one in six fights since 2008 — in September 2011, when Victor Ortiz inexplicably dropped his hands to apologize for a head butt. Mayweather sizes up his opponents, deftly eludes punches, then swoops in to rattle off a rapid-fire flurry of shots.

“Maidana had better have more than power, because he's fixin' to fight the ghost — the ghost that you see and now you don't,” said Mayweather's father, Floyd Sr., who once fought Sugar Ray Leonard. “You can't hit what you can't see.”

But Mayweather Jr. said he plans to go toe-to-toe with Maidana, and fight fans are waiting for that. More than 10,000 of those fans poured into the MGM Grand Garden Arena on Friday to watch the fighters weigh in. All the fighters on the card had their moment on the stage, flexing, smiling for the cameras and standing nose to nose with their opponents.

Mayweather, the highest-paid athlete in sports, is guaranteed a minimum of $32 million for this fight; Maidana gets at least $1.5 million. Both fighters also will share in the pay-per-view revenue if the event is a box-office success.

“I don't just go in there saying, ‘I want to win this belt,'” Mayweather said. “I want to look impressive when I go out there Saturday. I want to put on a good show. And we don't look for this fight to go the distance.

“This guy [Maidana is] talking about he's looking for the knockout, and I know we're not looking for the fight to go the distance. So it's going to be a helluva fight. I guarantee you that.”

Mayweather, in the third fight of a six-fight deal he signed with Showtime, points to Maidana's 80% knockout rate to quiet critics who say he's hand-picking opponents who won't threaten his unblemished record. Since 2009, Mayweather has been accused of ducking a superfight with Manny Pacquiao, although that dream bout lost some luster after Pacquiao was defeated twice in 2012.

“I want [Maidana] to bring his best,” Mayweather said. “Because if he does, he may be the first guy to actually make me dig in my bag of tricks and pull out my A game. Because my whole career, all I've had to use is my D and C game to beat every guy. I've never had to use an A game or a B game. We'll just have to see.”

Maidana, whose last loss came to Devon Alexander in February 2012, has won four fights in a row since switching trainers to the highly regarded Robert Garcia, who trains fighters in his Oxnard gym.

“I'm better now that I've been working with Robert Garcia,” Maidana said, with Garcia interpreting. “I feel much better. My punches are being thrown in a better location and with precision.”

Khan, for one, has firsthand experience with Maidana, whom he defeated by unanimous decision in 2010. Not surprisingly, Khan has studied Mayweather too, and is most likely Mayweather's next opponent if both win tonight.

“It will be a good fight,” Khan said of Mayweather-Maidana. “Both fighters are tough, strong. Mayweather has the speed, movement and the skills. Then you've got Maidana who has the power and the pressure. It's going to be a close fight after the first couple of rounds, [but] as Mayweather starts seeing him a little better, after four or five rounds it will be all Mayweather. He'll work him out, and I think he'll get a good win.”

Mayweather, a promoter at heart, isn't ready to dismiss the intrigue so quickly.

“I look at his last four fights; he's done a superb job,” Mayweather said. “He's the guy that we chose, so I can't sleep on this guy.”

sam.farmer@latimes.com