Is Mosley-Mayweather the next mega-fight?

Certainly, the bows to the record-setting Staples Center crowd were a treat, but it was minutes later in a quieter celebration that Shane Mosley received what qualified as the best ovation of all.

His beaming promoter, Richard Schaefer, hugged Mosley and whispered into his ear: “I will start having conversations with Team Mayweather tomorrow morning,” Schaefer said.

And just like that, Mosley’s intense wish to end his career on his terms, by remaining involved in what he calls “mega-fights,” had come true.

Thirty-seven-year-old boxers don’t always have that luxury, but Pomona’s Mosley (46-5, 39 knockouts) earned it Saturday night, dominating Tijuana’s Antonio Margarito. He won every round on one judge’s scorecard and pummeled the younger Margarito to win by ninth-round TKO and gain his fifth world title by wresting the World Boxing Assn. welterweight title from the champion, who kept the belt for only this one defense.

“The only right word for this was spectacular,” Schaefer said. “Shane told me, ‘Believe in us,’ and there was no question he believed in himself. He turned back the clock.”

Producing an unexpectedly spirited, vibrant effort, Mosley possessed a hand-speed mismatch against Margarito and landed a steady, damaging barrage of overhand rights and left hooks while moving easily away from the champion’s attempts to impose his formidable power.

He credited new trainer Nazim Richardson’s guidance and training regimen in Big Bear and also had plenty of incentive to take frustrations out on Margarito. Mosley’s marriage is ending, he’s involved in two BALCO-related lawsuits over his past steroid use and he walked into the ring amid media speculation that he was nearly finished. “I have a chip on my shoulder to be competitive,” Mosley said.

It didn’t look as if it was more than eight years after Mosley’s last fight at Staples, that upset over Oscar De La Hoya best remembered by the Pomona boxer’s continued late-round ability to beat his then-rival Golden Boy to the punch. It looked more like eight weeks later.

“I was just getting caught,” Margarito said. “Over and over.”

Now, with no rematch clause obligation to Margarito, Mosley says, “whatever person steps in front of me is a mega-fight, and that’s what I’ve always wanted.”

He’d like to avenge a November 2007 loss to Miguel Cotto. Yet Schaefer asked, “How does [unbeaten] Floyd Mayweather Jr. sound?” Said Mosley: “Great.”

Contacted by The Times on Sunday morning, Mayweather Jr.’s manager, Leonard Ellerbe, essentially opened the negotiations this way: “Floyd is retired.”

It’s almost stupefying that Mosley-Mayweather hasn’t happened yet. Will it now? Mosley’s speed, power and boxing versus Mayweather’s speed, defense and savvy? Mayweather has said recently through his manager that he’s willing to end his “retirement” dating to December 2007. Schaefer said, “Let me talk to them first.”

The welterweight division is so loaded, counting Manny Pacquiao, Ricky Hatton, Paul Williams, Mayweather and Cotto as members, Mosley appears assured of landing another big one such as Saturday’s, when a record 20,000-plus packed Staples.

“You saw this . . . everyone came out,” Mosley said. “These are the kinds of fights I like to fight.”

Margarito, meanwhile, remains scheduled for a June 13 rematch with Cotto, perhaps at Staples Center, his promoter Bob Arum said.

“Margarito had an off night,” Arum said. “In boxing, you win, you lose. It’s like a pitcher throwing four shutouts in a row. He might lose the next one, but he’s still good.”

Margarito has more to worry about than how to rebound from the Mosley loss. Before the bout, his original hand wraps were removed and Mosley’s attorney said “flecks of a substance” that appeared to be like plaster of Paris were found on pads wrapped atop his fist. His hands were rewrapped, and the contents of the original wraps and the “flecks” were secured in a box.

The California State Athletic Commission will begin “investigating” the contents of Margarito’s hand wraps today in Sacramento, commission official William Douglas said Sunday.

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lance.pugmire@latimes.com