Gennady Golovkin says defending his world titles against Canelo Alvarez in his first fight in Las Vegas may be the most difficult bout of his career. 

"It is the biggest fight of my career," said Golovkin. "Canelo is the biggest champion and the biggest name out there."

Three-belt champion Golovkin and Alvarez will meet for middleweight supremacy at the T-Mobile Arena in Las Vegas on September 16.

The 35-year-old Golovkin told a news conference at Microsoft Theater in downtown Los Angeles on Monday that if he wants to establish a legacy in boxing he needs to beat the likes of Alvarez. 

"I need this fight to get back to boxing. I have been working hard in training every day," said Golovkin, who has fought in seven different countries and 22 cities but never in Las Vegas.

He is undefeated with a 37-0 record while Alvarez has only lost once in 51 fights (49-1-1). 

Promoter Tom Loeffler said WBC, IBF and IBO champion Golovkin is having no trouble getting motivated for this fight which is sold out. 

"He has the sparkle in his eye again," said Loeffler.

Alvarez, meanwhile, added that this fight will be on the same level as his 2013 bout against Floyd Mayweather which he lost by a decision.

"It is right there with Mayweather and possibly bigger. That fight taught me a lot. But this fight will bring out the best in me," said the 27-year-old Mexican.

"(Golovkin) is the most dangerous fighter at this moment. We want to show him that on this side, there is a lot more to give, too."

Meanwhile, Golovkin, of Kazakhstan, admitted he didn't see the Mayweather-Conor McGregor spectacle and being a boxing purist he feels he didn't miss anything. "I didn't watch it. I am too busy," he said. 

Five-division champion Mayweather won the novelty fight by a TKO in the 10th round to improve to a perfect 50-0 in his career in a one-sided bout that played out the way many had expected.

Golovkin's advice to McGregor, who was making his professional boxing debut, would be to not quit his day job. "McGregor in boxing, no. He's not a boxer. He is a UFC fighter."

Golovkin's promoter Loeffler said Mayweather shouldn't be allowed to include that fight in his official boxing results. 

- Asterisk needed -

"There should be two asterisks," said Loeffler of Mayweather, who could earn $200 million from the event.

"When you talk about breaking records you can't count that as a 50th fight. Just like when Muhammad Ali fought Inoki. It was a spectacle."

Loeffler was referring to another novelty event in 1976 when Ali battled Japanese professional wrestler Antonio Inoki in Tokyo.

Former world champion and Olympic gold medallist Oscar De La Hoya has been one of the biggest critics of Mayweather-McGregor from the start. De La Hoya, who promotes Alvarez, didn't pull any punches Monday when talking about the Mayweather-McGregor event.

"I thought it was a fraud," De La Hoya said. "Only Mayweather knows why it lasted 10 rounds."