Las Vegas (AFP) - Gennady Golovkin has travelled the globe winning boxing matches in 22 cities and seven different countries to earn his Las Vegas debut on Saturday (Sunday morning, Singapore time).

The 35-year-old Golovkin has waited years for the arrival of this career-defining super-fight against Mexico's biggest boxing star Canelo Alvarez.

It is also the three-belt champion's first fight in Las Vegas and it fittingly comes against the toughest opponent he has ever faced in a career which has been defined by a steady jab and explosive knockout power.

"The biggest day is coming," Golovkin said. "This is my game. My fight, I am the boss. I am the champion."

That was a mouthful from Golovkin.

All week long during the build up to Saturday's fight at the T-Mobile Arena for middleweight supremacy, the reserved Golovkin has said he prefers doing his talking in the ring.

When reporters asked him on Wednesday about the birth of his second child, which happened last Friday, he said, "Please don't ask me about my family. I am just focused on boxing."

His boxing career started in his native Kazakhstan. Growing up in a family of four boys, if he wasn't scrapping with his brothers at home, he was fighting much older and bigger kids in the streets.

He had his first professional fight in 2006 at age 24 after a superb amateur career which included a silver medal at the 2004 Athens Olympics.

Golovkin fought in Germany and Denmark before joining forces with trainer Abel Sanchez who taught him how to maximise his strengths.

Sanchez and Golovkin teamed up for fights in Panama, Kazakhstan, Germany and Ukraine before Golovkin made his American debut in 2012.

Golovkin's twin brother, Max, said Gennady is a very private person.

"Nobody knows about it because camp is always closed," Max said. "No one knows how dedicated and focused and concentrated he is."

Max knows Gennady better than anyone. They had an older brother, Vadim, who helped introduce them to the sport and another brother, Sergey, who took time to work with them as well.

Tragically both brothers were killed in separate incidents while serving with the Russian army.

The funeral for Vadim, who died first, was held with an empty casket. The family is still trying to find out the details of what happened.

Gennady named his first child, a boy, after him. Max is also on Gennady's mind when he fights.

The family didn't have much money so when Gennady turned 18, he was the one they picked to pursue a boxing career.

"They chose Gennady to continue his career," Max said. When you consider Gennady's difficult journey to the pinnacle of his profession, it is easy to see why he insists on taking nothing for granted.

They say styles make fights and this one has the ingredients to be the start of a special rivalry.

Alvarez insisted on a rematch clause for the fight which some are hoping is the beginning of boxing's newest trilogy like Manny Pacquiao-Juan Manuel Marquez, Erik Morales and Marco Antonio Barrera and Micky Ward versus Arturo Gatti.

Golovkin says he is willing to take on all comers and cannot wait to get into the ring with Canelo, comparing the excitement to being with a new lover.

"It is like you are going with your new girlfriend. Oh yeah," he said.