Now that it’s official that Mexican stars Canelo Alvarez and Julio Cesar Chavez Jr. will meet in a huge all-Mexican showdown on May 6 (HBO PPV) -- Cinco de Mayo weekend -- at a site to be determined, one of the central storylines sure to be dissected until fight night is the question of weight.

The 12-round bout was contracted at 164.5 pounds, 9.5 pounds heavier than Alvarez has ever fought at, as a concession to the bigger Chavez, who has had problems making even the super middleweight limit of 168 pounds in recent years.

Chavez (50-2-1, 32 KOs) has missed weight multiple times and weighed in at 167.5 or heavier for his past five fights dating to 2013. There was simply no way he could agree to fight any lower than he did.

Alvarez (48-1-1, 34 KOs), who won a 154-pound title from Liam Smith in his last fight in September, agreed to make the big leap in weight. The sides went back and forth on weight a lot during the negotiations until Alvarez finally gave in at 164.5.

"He talks too much about me. He's talked bad about me and criticized me so many times. I will prove to him in the ring who's the better man." Canelo Alvarez

Asked on Friday after the fight was finalized why he agreed to move up so much, Alvarez said the prospect of such a big rivalry fight was too much to pass up.

“I think what convinced me to make the move was the fight itself, which is one of the biggest, if not the biggest, in the history of Mexico,” Alvarez told boxing reporters through a translator on a teleconference to announce the bout. “That’s what intrigued me. The significance of the fight is what convinced me to make the move.”

Had Chavez turned down Golden Boy Promotions' final offer, Alvarez would have challenged middleweight titleholder Billy Joe Saunders (24-0, 12 KOs) instead. Golden Boy and Saunders promoter Frank Warren already had made a deal but Warren knew they were the backup plan in the event Chavez didn’t take the fight.

“Obviously, Saunders was there,” Golden Boy president Eric Gomez said. “We had discussions. Canelo became mandatory for that title. [Former middleweight titlist David] Lemieux was interested in fighting Canelo as well. But this is the fight Canelo wanted and the one [Golden Boy CEO] Oscar [De La Hoya] wanted as well.”

"This fight transcends weights and championships. It's probably the biggest fight in Mexican history." Golden Boy president Eric Gomez

Chavez has nearly four months to slowly and properly make the weight. His camp said he is prepared to put in the hard work to make it. If either fighter misses weight, it will cost the guilty party $1 million per pound, sources involved in the fight told ESPN.

Alvarez said he hopes he faces the best version of Chavez possible.

“I just hope he trains well and gets ready for this fight,” Alvarez said. “I will be ready to face the best possible Chavez. After this fight I don’t want any excuses when I beat him. I want him to train hard and be the best possible Chavez.”

Alvarez said he also saw the opportunity to make the fight as a chance to shut down a rival who has had plenty of negative comments about Alvarez over the years. Make no mistake -- these guys do not care for each other.

“Plenty of rivalry,” Alvarez said. “He talks too much about me. He’s talked bad about me and criticized me so many times. I will prove to him in the ring who’s the better man.”

Former middleweight titleholder Julio Cesar Chavez Jr. has had trouble making the super middleweight limit in the past. Esther Lin/Showtime

Should Alvarez win and unified middleweight titlist Gennady Golovkin defeat Daniel Jacobs in their March 18 HBO PPV fight at New York’s Madison Square Garden, Alvarez and Golovkin likely will square off in a huge fight in September.

Alvarez would fight Golovkin at 160 pounds. Gomez said Alvarez’s decision to take on Chavez ahead of the potential Golovkin fight is solid preparation for that fight.

“It’s a bigger guy, he’s right-handed and not a guy who will box or run,” Gomez said of Chavez. “I think it prepares [Alvarez] very well [for Golovkin]. It’s not a similar style to GGG because GGG is a better boxer, but Chavez is a bigger guy in front of him who will be throwing bombs.”

Asked about probable criticism coming their way for insisting that Alvarez needed to work his way up to 160 before fighting Golovkin -- yet agreeing to go all the way to 164.5 to fight Chavez first -- Gomez was blunt.

“This fight transcends weights and championships,” Gomez said. “It’s probably the biggest fight in Mexican history.”