For young fighters on the rise, an important milestone is facing and defeating a former world champion. For Mexican sensation Saul “Canelo” Alvarez, that time is now.

The 20-year-old Alvarez, one of the most heralded Mexican prospects in years, will face former welterweight world champion Carlos Baldomir on Sept. 18 at the Staples Center in Los Angeles, Golden Boy Promotions announced Tuesday.

Alvarez and Baldomir will square off in a junior middleweight bout — with a contract maximum weight of 151 pounds — in the co-featured fight on the HBO PPV card headlined by the junior middleweight bout between Shane Mosley and Sergio Mora.

With the card, which is dubbed “200: Celebrate And Dominate,” taking place on the weekend of the Mexican Independence Day bicentennial, Golden Boy wanted to showcase Alvarez, whom it signed earlier this year, in the United States, where it hopes he can build a similar following to the one he has in Mexico. At home, Alvarez draws massive television ratings and sells out arenas.

“When Alvarez recently fought in Mexico, there was an average between six and eight people per home watching this fight,” said Golden Boy CEO Richard Schaefer, referring to statistics he said he received from Mexican network Televisa. “The fight got a 17.8 rating, which is equivalent to 600,000 homes watched by 60 million people.

“Canelo has reached superstar status in Mexico. The ratings he gets on the national Mexican broadcaster, Televisa, are unheard off and in line with what the national soccer team gets.”

Although Alvarez (33-0-1, 25 KOs) enjoys fighting in Mexico, especially in his hometown of Guadalajara, he’s excited to be on the card in the United States.

“I’m glad to be on such an important card with such good fighters,” Alvarez said. “It’s business as usual when I step into the ring. I fight with desire. I hope everyone comes out that night to watch because this is a really exciting night of boxing.”

Said Jose Reynoso, Alvarez’s manager and trainer: “This is a very important date. As Mexicans, we are celebrating the bicentennial of Mexican Independence. [Alvarez] is No. 1 in Mexico and now we want to conquer the world. A big part of that is being successful in L.A.”

In 39-year-old Baldomir (45-12-6, 14 KOs), Alvarez will face the most experienced opponent of his career, although he has lost three of his last five fights.

Baldomir, who once sold feather dusters on the streets of Santa Fe in his native Argentina, emerged from obscurity in 2006 when he pulled massive back-to-back upsets and earned the nickname “Cinderella Man.”

First, he scored a clear unanimous decision against Zab Judah, in Judah’s hometown of New York, to win the undisputed welterweight title. Then he knocked out Arturo Gatti in the ninth round on Gatti’s turf in Atlantic City, N.J., to retain the title in another shocker before finally seeing his magical year come to an end with a virtual shutout loss to Floyd Mayweather Jr.

Baldomir, who has only been stopped once early in his career, is coming off a fourth-round knockout of journeyman Jairo Jesus Siris in November in Argentina.

“Carlos Baldomir is a fighter with an iron will and iron chin. He will come to Los Angeles and try to derail the fast rise of Canelo Alvarez,” Schaefer said. “He is on a mission to come and capture the American market and display his talent and excitement at Staples Center on Sept. 18. He realizes that Los Angeles is the largest Mexican market outside of Mexico and wants to come and show what he is all about.”

Said Golden Boy president Oscar De La Hoya: “I walked the streets myself the other day in Mexico where I watched Alvarez fight [on July 10]. I was asking people from all walks of life, ‘Have you heard of Canelo Alvarez?’ And everyone answers with a glowing face [and said], ‘He’s our next promise. He’s our next guy.'”

In the scheduled 12-round main event, former three-division champ Mosley (46-6, 39 KOs) will fight for the first time since losing a lopsided decision to Mayweather on May 1 when he meets Mexican-American and fellow Southern California native Mora (22-1-1, 6 KOs). Mora, a former junior middleweight titlist best known for winning the first season of “The Contender” reality series, moved up to middleweight following his rematch title loss to the late Vernon Forrest, but is returning to 154 pounds for the high-profile fight with Mosley.

Also on the undercard, 23-year-old junior welterweight contender Victor Ortiz (27-2-1, 21 KOs), the 2008 ESPN.com prospect of the year, will face former titlist Vivian Harris (29-4-1, 19 KOs).

Dan Rafael is ESPN.com’s boxing writer.