Shane Mosley assesses Canelo-Golovkin matchup

There may be no better person to assess the Gennady Golovkin-Canelo Alvarez Sept. 15 rematch at T-Mobile Arena in Las Vegas than former three-division champion Shane Mosley.

Mosley has sparred with middleweight champion Golovkin (38-0-1, 34 knockouts) and former two-division champion Alvarez (49-1-2, 34 KOs) in Big Bear, and dropped a unanimous decision to Alvarez in 2012.

Like Alvarez, Mosley had to work hard to rehabilitate his image from performance-enhancing drug use. He admitted in grand jury testimony to using banned substances leading up to a narrow 2003 victory by unanimous decision over Oscar De La Hoya.

And like Golovkin, Mosley pursued the idea that beating the most popular fighter in the world would elevate the winner to the same distinction.

“I think ‘Triple-G’ will get that because he’s already big himself,” said Mosley, a recent inductee to the Nevada Boxing Hall of Fame. “Gennady’s a little bit bigger than I was as a lightweight going to welterweight. After I beat Oscar [in 2000 at Staples Center] I still had to prove myself.”

Without the years of prized publicity that East L.A.’s De La Hoya gained by winning a 1992 Olympic gold medal, Mosley grinded through the competitive Southern California pro boxing circuit to raise his profile.

“Oscar had a big jump start of winning the gold medal. I remember beating [Narciso Valenzuela], a journeyman Oscar had fought, and made $500,000 for. I fought him the fight after for $5,000 … ,” Mosley said. “The East Coast writers saw me and wondered why everyone on the West Coast wasn’t writing about me.

“Don’t get me wrong, Oscar was really good and lived up to his reputation by being sharp and knocking guys out. But I was pretty good too. I’m not sure I got the bang for the buck that was expected [by beating De La Hoya in 2000], but I did elevate my career from what it was.”

Golovkin fought Alvarez to a draw last September — a controversial outcome because of the one-sided scorecard of judge Adalaide Byrd in favor of Alvarez and a seventh-round vote for Alvarez by judge Don Trella that differed from the other scorers. The performance boosted Golovkin’s profile, and he would get a further lift if he breaks the middleweight record of 21 consecutive title matches without a loss.

Golovkin maintains he’s not expecting Alvarez’s large fan base to switch sides should the Kazakh fighter win their rematch.

“I’m not thinking about my popularity at all,” he said. “What’s interesting to me is to experience this fight at such a high level.”

Golovkin also wants to punish his rival for two positive tests for the banned endurance-building substance Clenbuterol in February, which resulted in a six-month suspension for Alvarez and forced the cancellation of their original May 5 date for this fight.

The controversy has cast Alvarez in a sinister light for the first time, exactly where Mosley found himself when it was revealed by federal officials, and later confirmed by BALCO founder Victor Conte, that Mosley used performance-enhancing drugs before his 2003 rematch with De La Hoya in Las Vegas.

The stigma weighed on Mosley, and he’s sure it’s bothering Alvarez.

“Boxing’s a mental thing, so if you have a lot of negativity, and people are saying different things, that can hurt you,” he said. “I’m not saying Canelo won’t look the same as the first fight. But mentally it can beat you down, and you need to overcome that.

“The strength of the mind is what makes fighters great. You’ve got to rely on your self-confidence and the team has to keep you up. You have to work hard, stay focused and mentally strong and believe you are who you are.”

Mosley achieved a redemptive victory in 2009, when he returned to Staples Center to knock out Antonio Margarito after Margarito had plaster-caked hand wraps confiscated just before the bout.

Mosley is not sure what to think about Alvarez’s account that the Clenbuterol entered his body when he ate contaminated meat in Mexico.

“I kind of do believe it, but you don’t know who he has around him to help give him the food that had more vitamins in it,” Mosley said. “Maybe it wasn’t the meat from the market. Maybe there was doctor work on the side. Who’s in his camp?

“I don’t think it’s made that much of a difference, but we will see. When I fought Oscar the first time, I thought I clearly beat him. [Post-PED in 2003], it was really close. I thought, ‘Oh well …’ I fought worse. The big conspiracy … it didn’t make that big of a difference.”

Mosley, who engaged in high-profile rematches with De La Hoya, Hall of Famer Winky Wright, Fernando Vargas and Vernon Forrest, said it’s important to “rely on your strong points and display them early” in the second bout.

Shane Mosley, left, Oscar De La Hoya and Canelo Alvarez in 2012.

(Johan Ordonez / AFP/Getty Images)

“As the fight goes on, it’s easier to get done what you need to get done. Oscar moved around in the second fight and that made it difficult for me. Against Vargas, I was leaner, and that speed made it easier for me to knock him out,” Mosley said. “Repeat your strengths, and do them better. Triple-G might know he can take Canelo’s best punch. That’s why Triple-G has to jump on him. I think Canelo can break down.”

Mosley would make Golovkin the favorite.

“He might have some more age, but it’s a hard fight for Canelo because GGG is too big and strong,” Mosley said. “I believe he’ll walk Canelo down and have his way with him if he turns it on earlier.”

Mosley said a knockout victory is “a possibility in the later rounds if he applies pressure early and makes Canelo work every bit of the rounds. It’s hard for Canelo to fight the whole fight. He fights when he wants to.”

However, Alvarez may be motivated by the opportunity to win and declare he did so while being tested throughout training.

“It’d be a testament to his overall boxing skills and mental strength,” Mosley said. “He has to do everything right to be able to outbox and beat Triple-G, because he is coming and he’s serious.”

lance.pugmire@latimes.com

Twitter: @latimespugmire