Floyd Mayweather v Saul Alvarez preivew: How ginger kid went from Mexico's streets to the MGM in Las Vegas

It is far too easy to create a romantic fiction of Saul Alvarez's early years as a pugilist, when the chunky ginger kid was fighting men from the age of 15 in tiny Mexican towns, and forget just how good he is.

Alvarez survived the obscure apprenticeship, was spotted at 18, after 22 fights without defeat, by a member of Oscar de la Hoya's company, Golden Boy, and a deal was done. That was in 2008 and now, 21 fights, including six world title fights, later, Alvarez is close to making a purse of $10m (£6.4m) for Saturday's light-middleweight showdown with Floyd Mayweather at the MGM in Las Vegas.

"He had an amazing following in Mexico and they crossed the border to watch him fight, thousands crossed the border," said De La Hoya, who revealed this week that he will not be ringside for the fight but will instead be in rehab, battling his drink and drug problems.

"We had only just heard about him, it was like the rumours were growing and then thousands were showing up; they had on T-shirts with his picture and they chanted his name. It was crazy."

In April of this year, 39,000 paid to watch Alvarez fight in San Antonio, Texas, for a flawless display of power and timing against Austin Trout, who lost for the first time in 27 fights. Yet the Mexican always seems to look embarrassed at the end of fights as the ring fills with cheerleaders and relieved backers.

In the ring that night was Alvarez's brother Rigoberto, one of six Alvarez boys and a former world champion who had lost his title to Trout. "I was the youngest, they all went to the gym and I just went with them, but they never made it easy," said Saul, who has just turned 23.

It was in the days before the Trout fight that an incident from 2011 threatened briefly to taint the boxer's wholesome image. An arrest warrant was issued after it was alleged that he had fractured another boxer's jaw in a scrap over a woman – Alvarez denied the charge. The fight still happened and Alvarez returned to Mexico City and enjoyed a 45-minute audience with President Enrique Pena Nieto. The meeting seemed to secure Alvarez's position as one of Mexico's "untouchables" and the warrant is simply gathering dust.

"He's a private man," insisted Jose "Chepo" Reynoso, who has been with him for over a decade. "He's not a big talker, never was." Neither is Reynoso, by the way, but he has crafted quality fighters in his gym and knows how to let Mexico's child boxers develop into men before they start blowing bubbles prematurely.

There is a murky side to the world of underage boxers and their fights in Mexican tenements, but Alvarez had won a national amateur title at 15 before turning professional.He was not without some boxing knowledge having won 44 of his 46 amateur fights, however he left school the moment he started punching for pay.

Alvarez is known as "Canelo", which is Spanish for cinnamon, because of his red hair and refuses to say anything bad about any of his opponents, which has clearly frustrated Mayweather. "He doesn't speak a lot of English, so why should I say anything to him – he doesn't understand," the American said. The two fighters were on a 12-city promotional tour and Alvarez claimed he enjoyed it. Ricky Hatton, who fought Mayweather in 2007, went to five cities and was less impressed: "I was ready to kill him, he drove me crazy," Hatton said. Alvarez, when asked about his time with Mayweather, replied in his high-pitched voice: "No problem."

Alvarez's shyness, impassive face and humility form a perfect counter to his ruthless skills inside the ropes. "He just gets to where you are going, he cuts the ring down and never wastes any punches," said Ryan Rhodes, a former British champion from Sheffield, who was stopped in the 12th and last round of a world-title fight in 2011.

In some ways his style is a mixture of the old and the familiar, which is perfect. He has been described as having the attitude of an American, the looks of an Irishman and the fighting style of a Mexican.

Now the ginger kid, taunted for so long as a child because of his hair, is Mexico's main sporting attraction with fights that attract as much as 35 per cent of the television audience share.

His girlfriend is a former Miss Mexico Universe and Alvarez still lives with his mother in Guadalajara; they have left the ugly apartment complex for a penthouse in the most expensive part of town. On Saturday he will start as the underdog, fight his heart out roared on by record crowds and, win or lose, leave Las Vegas a very wealthy boy.