Alvarez and Golovkin were scheduled to meet on May 5 on HBO PPV at T-Mobile Arena in Las Vegas in a rematch of the controversial draw most thought Golovkin won in September. However, Alvarez twice tested positive for the banned performance-enhancing drug clenbuterol in random urine tests conducted by the Voluntary Anti-Doping Association in his hometown of Guadalajara, Mexico, on Feb. 17 and Feb. 20.

"We're going to have to cancel the May 5 rematch," Golden Boy Promotions president Eric Gomez said at the beginning of a news conference at the company's offices in downtown Los Angeles. "As you all know there is a hearing on April 18 and it's extremely unlikely this will get properly resolved by then and we need enough time to promote this fight.

"Additionally, given the current regulations in Nevada we have been advised, and it is unfortunate, that Canelo won't be cleared to fight in May. We are hopeful this matter will be resolved and we are hoping Canelo will be cleared so we can reschedule the fight for August or September."

Alvarez proclaimed himself a clean fighter but said he was ready to take his punishment from the NSAC.

"I am truly shocked about what has happened and for those who have doubts and suspicions about my integrity, I have always been and always will be clean fighter," Alvarez, speaking through a translator, said in his first public comments about the situation other than a brief statement he made two weeks ago when the positive test results were announced.

"I want to apologize to HBO, Tecate and Hennessy and all my other sponsors, the media and to everyone who is involved in the promotion of this event, and especially to the fans. I respect this sport. I will always be a clean fighter."

Alvarez noticeably did not apologize to Golovkin, who last week accused him of purposely using performance-enhancing drugs during his training for the rematch as well as for the first fight, though he never failed a test prior to the bout last year.

"To be honest, what Golovkin or his team say doesn't bother me at all because, No. 1, they are not doctors, not experts," Alvarez said. "I don't pay attention to them. It sounds more like an excuse that he doesn't want to fight me or he's scared."

Golden Boy CEO Oscar De La Hoya stood up for his marquee fighter.

"I want to speak to Canelo's character," De La Hoya said. "I can assure you that both inside and outside the ring Canelo has always displayed a professionalism and commitment all too absent in the sport. I have known Canelo since he was a teenager and [he has] handled himself with grace and class and showed respect for the sport. He's the model for what we want the best in our sport to be.

"I sincerely hope that given his unblemished record of having never tested positive in more than 90 tests in and out of competition, you would be willing to give Canelo fair consideration."

Alvarez claimed the positive tests were from eating contaminated beef in Mexico, where that has been a problem for many athletes because clenbuterol is often used by farmers in cattle feed. However, Nevada commission rules are clear that the athlete is responsible for what is in his system, whether it is there on purpose or by accident.

Alvarez reiterated his claim of having eaten contaminated beef.

"I want to clarify the situation. I have always done tests with VADA before my fights. They are voluntary," he said. "I have always agreed to them before my fights and they have always come back negative. I am a clean fighter. On this occasion the results showed small traces of clenbuterol. How did this happen, I don't know. Unfortunately, there is a public problem in my country of Mexico. Football, cycling, soccer, boxing -- people have tested positive for clenbuterol. This can be transmitted through meat in Mexico. Contaminated meat is what caused this. That is my statement. This has happened in all sports."

To hammer home Alvarez's point about meat contamination, Golden Boy had Dr. Miguel Angel Nazul, the vice president of the Mexican Federation of Sports Medicine, speak at length about the issue in Mexico.

Alvarez (49-1-2, 34 KOs), 27, elected to withdraw from the fight and perhaps create some goodwill with the commission before it is likely to suspend him for at least one year at a hearing scheduled for April 18 in Las Vegas.

This is Alvarez's first offense, which usually nets a one-year suspension, but if he cooperates with the commission it is within its rules to reduce the suspension to six months. If Alvarez's suspension is cut to six months -- and it is retroactive to Feb. 17, the date of the first positive test -- he would eligible to box again on Aug. 18. That would allow for the rematch with Golovkin to be rescheduled on the Mexican Independence Day weekend in mid-September, which is when they had their fight last year.

Since the positive tests, Alvarez moved his training camp to San Diego -- where he usually trains -- and has been undergoing more rigorous VADA testing with several negative results since the positive results were delivered.

"I respect the Nevada State Athletic Commission and understand there are certain penalties and sanctions even for unintentional [positive] results," Alvarez said. "The reality is that unfortunately the rematch will have to wait a little longer. I am truly disappointed and upset that I will not be able to take part in the rematch [on May 5]. I was very much looking forward to the fight and looked forward to proving I am the best in the world.

"I am willing to do whatever [the Nevada commission requests to prove I am a clean fighter. I will do everything in my power to prove that I never intentionally ingested clenbuterol. I have nothing to hide. I wanted to be open and transparent in this process. Because of the respect I have for this sport, I will do whatever I can to show I have not taken this and want to prove I am a clean fighter."

Alvarez said without question he wants to fight Golovkin again as soon as he is eligible.

"That is the fight I want and it's the fight I want to give the fans," he said. "As soon as I get the green light, that's the fight I want."

Golovkin (37-0-1, 33 KOs), 35, still plans to fight an opponent to be determined on May 5 -- with the fight moving to the smaller MGM Grand Garden Arena -- and would have to retain his belts to keep the prospect of the fall rematch alive.

"I am looking forward to returning to Las Vegas for my 20th title defense and headlining my first Cinco de Mayo event on May 5," Golovkin said in a statement provided to ESPN. "It is time for less drama and more fighting."

Alvarez took some questions but his attorney, Ricardo Cestero, was careful in what he would allow Alvarez to answer. Cestero said he has given the Nevada commission evidence -- such as receipts for purchased meat or restaurant receipts -- to prove what Alvarez had eaten prior to the positive tests.

"It saddens me people are accusing me of doing something improper," Alvarez said. "I am proud of the career I've had. From here on out I will take precautions before future fights and make sure this never again happens. I am ready for what comes in the future."