GUADALAJARA - Canelo Alvarez defends his undisputed super middleweight championship Saturday vs. John Ryder before 50,000-plus fans at Akron Stadium - his first fight in Mexico in nearly 12 years - but already, boxing's top star is plotting his next bout.

Alvarez (58-2-2, 39 KOs) plans to fight again on Sept. 16 (he routinely headlines on Cinco De Mayo Weekend and Mexican Independence Day Weekend) and there's only one matchup he has in mind: a rematch with light heavyweight champion Dmitry Bivol.

When they met last May, Russia's Bivol (21-0, 11 KOs) scored the upset to hand Canelo his second career defeat in a rout. That was Alvarez's second fight at 175 pounds, and afterward, he returned to defend his four 168-pound titles with a victory over rival Gennadiy Golovkin to close out their trilogy.

Canelo said on Thursday that he's only interested in the rematch taking place at 175 pounds, while Bivol told ESPN that he will only accept the return bout for Alvarez's undisputed championship at 168 pounds.

"I want the same terms, the same everything as the last fight," Canelo, 32, told ESPN. "But right now, I'm focused 100% on John Rider because he's boxing, and you never know. But the goal is to have the rematch with Bivol in the same terms. ...

"I think I'm better than him - that's it. If you see the first five rounds, six rounds, I dominate the fight. But then I get tired, of course, because I don't train at my 100%."

Alvarez said he dealt with a nagging left wrist injury while training for his November 2021 fight with Caleb Plant, an 11th-round KO victory to become undisputed champion. That ailment lingered throughout his fights vs. Bivol and GGG last year to the point, Alvarez said, where it pained him just to glove up in the locker room before the bouts.

Canelo said his high pain tolerance allowed him to push through - "as a fighter I say I can do one more fight" - before he eventually underwent surgery in October.

The repaired hand gives him confidence he can defeat Bivol at 175 pounds. Bivol, who's never competed under 173 pounds, believes he can beat Canelo at his natural weight - 168 pounds.

In a sport where each side always tries to gain a competitive advantage and catchweights are common, this is an unusual turn, but Alvarez and Bivol have their reasons.

"Everyone is going to f---ing start saying, 'Oh, but he brought him down [in weight], that's why [Bivol] lost," said Alvarez, ESPN's No. 5 pound-for-pound boxer. "But they didn't say anything when I went up [in weight]."

Bivol, ESPN's No. 6 pound-for-pound boxer, has a similar argument.

"In the last fight, he went up into my weight class, but he's fought in that weight class before (a 2019 KO victory over Sergey Kovalev) and we fought at 175 and I beat him," said Bivol, 32. "So now I'm willing to take a risk and go to 168 because it's a motivation for me to try to fight for all the titles at 168. Otherwise, he's had two other fights [in between].

"Why should I even do the rematch at 175? What is the challenge or what is the motivation for me if I've already beaten him at that weight class? And I don't think we should worry about who thinks what. It's really about what we want; what each of us wants. And I think he wants to win and if he can win, he might have a better chance at 168 because he said that that's his weight class. And for me, there should be some motivation and some challenge."

If Alvarez won't concede to the fight taking place at 168 pounds, Bivol's manager, Vadim Kornilov, said they'll focus on a bout against Artur Beterbiev for the undisputed 175-pound championship.

"He wants to take a step up and the step up is either fighting Beterbiev, which is really what he wants ... or a new challenge with Canelo," Kornilov said. "It has to make sense. There's no reason we have to agree to everything, especially after the last fight was a blowout. ... We want our fans to be satisfied as well and to know that we can beat him either way. It's not about the hand, it's not about the weight class. We don't want any excuses."

Kornilov believes the real reason Alvarez wants the fight at 175 pounds is so he can return to 168 pounds with all his titles intact like last time, along with another reason.

"[Canelo] wants to be able to have an excuse in case he loses," Kornilov said. "He wants to say, 'oh, that's not my weight class.' ... We're not going to do the fight at 175. ... Our main goal is to go for undisputed and it's either Beterbiev at 175 for undisputed or Canelo."

Besides, Kornilov said, if Alvarez defeats Bivol at 168, they can always do a trilogy fight at 175. But first, Canelo must push past Ryder on Saturday - Alvarez is a -2000 favorite, per Caesars Sports - and emerge uninjured. After that, Hearn told ESPN, they'll "open real negotiations for the Canelo-Bivol fight in September."

It appears to be a fait accompli that Alvarez and Bivol will meet for a second time on Sept. 16, but one side will have to give in on the weight.

"I don't like the fight at 168 for a few reasons," Hearn said. "No. 1 is I don't think a fighter like Dmitry Bivol should come down to 168 for the first time in his career for a fight like that. And I don't think knowing Canelo that he will want to gain victory by people saying he depleted Bivol in the fight. ...

"The only way he's going to get the credit is to avenge the defeat on the same terms that he lost. ... It's intriguing at 175 cause you go, '[Canelo] just can't win.' When does Canelo go into a fight where you go 'he can't win?' ...

"I think at 168 it's a 50-50 fight; I think Canelo's the favorite actually. But at '75 Bivol's a massive favorite."

One other issue at play: WBC president Mauricio Suliman said on Monday that Bivol is ineligible to challenge for the organization's title due to ongoing sanctions for Russian and Belarusian fighters.

Bivol holds the WBA light heavyweight title, but if he fights Canelo at 168 pounds or Beterbiev at 175, the undisputed championship wouldn't be on the line unless the WBC changes its stance.

"I was disappointed with Mauricio's comments," Hearn said. "I know it's a delicate situation but Dmitry Bivol is a class man and I don't see why his career should be affected by the actions of others."

Beterbiev, a native of Russia who lives in Quebec, hasn't been impacted by the WBC's sanctions. He's set to defend his three titles this summer against Callum Smith.