SAN JOSE -- Robert "The Ghost" Guerrero finally got the fight he wanted.

The Gilroy welterweight will face Floyd Mayweather Jr. on May 4 in a Showtime bout, probably at the MGM Grand Garden Arena in Las Vegas, promoters announced Tuesday. After years of chasing big-game names such as Manny Pacquiao and Juan Manuel Marquez, Guerrero landed the biggest name of all.

"I'm ending your career on May 4," he said in a tweet directed at Mayweather, "so start saving that MONEY."

Mayweather, who turns 36 Sunday, is 43-0 with 26 knockouts but hasn't fought since defeating Miguel Cotto on May 5, a span that included a two-month jail term for domestic battery.

Guerrero, 29, the WBC's interim welterweight champion, has a record of 31-1-1 with 18 knockouts.

"People are going to see why Manny Pacquiao avoided us and why Juan Manuel Marquez avoided us," said Bob Santos, the man who has served as Guerrero's trainer since the fighter was a teen. "Floyd better enjoy that undefeated record, because he has two months to go and he's going to get that first loss."

Richard Schaefer, an executive with Golden Boy Promotions, didn't discount the possibility of an upset. He said Guerrero has a strong chance because he is younger, "fast, strong, extremely skilled and has an amazing chin."

At the same time, Schaefer said: "Mayweather feels it is going be an easy fight for him."

It's a big fight for Mayweather, who ended a 23-fight association with HBO on Tuesday to sign a six-bout deal with Showtime. Showtime executive Stephen Espinoza, in an interview with USA Today, called it the biggest deal for his network since signing Mike Tyson in his prime.

But in these parts, the biggest deal was Guerrero. One of his Bay Area counterparts, Oakland super middleweight champ Andre Ward, congratulated Guerrero and expressed pride in the Bay Area, which also boasts another top-flight fighter in San Leandro's Nonito Donaire.

Ward, whose burgeoning career is on hold while he recovers from a shoulder injury, said: "Robert talked himself and earned himself this position. Unfortunately in boxing you don't get heard unless you make some noise. He made it clear he wanted Mayweather and Mayweather is who he got."

Schaefer said the "noise" didn't factor into the matchup.

"Floyd is not moved by these tactics," he said. "He told Robert to go and earn it. That's exactly what he did."

It has been a long, hard climb for Guerrero. He not only struggled to land big-name fights but also put his career on hold in 2007 while his wife, Casey, battled leukemia. She is healthy now, her life saved when a bone marrow match was found with a woman in Germany.

His family trials put the Mayweather fight into context for Guerrero.

"He knows what it is like to be in pressurized situations," Santos said. "With the mother of his children as close as you can be on a death bed, there is nothing too big to handle because there is nothing bigger than that."

The boxer's back story is why Schaefer said Guerrero will burst into the American consciousness leading to the match.

"The American public will get to know Robert Guerrero," he said. "And America is going to root for Robert Guerrero."