This is serious for De La Hoya

From the first news conference announcing the fight, Steve Forbes has talked about being “overlooked” by Oscar De La Hoya for tonight’s non-title 150-pound fight at the Home Depot Center.

That may be a powerful motivational tool. Yet almost everything De La Hoya has done -- from selecting Forbes over two other contenders to showing up in Los Angeles this week at the welterweight limit of 147 pounds when he can afford to be plumper -- speaks to the Golden Boy’s stated fierce desire to treat Forbes, a tough opponent, seriously.

No one denies, however, that this fight is in preparation for De La Hoya’s Sept. 20 rematch with unbeaten Floyd Mayweather Jr.

“To the extent that Oscar is setting up that fight with Floyd, yes, he’s right that Oscar’s expecting to win,” said Eric Gomez, the Golden Boy Promotions matchmaker. “What Stevie doesn’t understand is that Oscar has been through this [tune-up fight] before, and he remembers he didn’t do well.

“So he’s conditioned his mind, not only on the fact he wants revenge against Mayweather, but that he needs to be sharp against Stevie. He’s locked and loaded.”

De La Hoya (38-5, 30 knockouts) insists he will no way duplicate his sluggish performance in 2004 against Felix Sturm, a middleweight who some at ringside felt won the fight that came three months before De La Hoya’s knockout loss to Bernard Hopkins. All three judges scored the bout 115-113 in De La Hoya’s favor.

“I did look past Felix Sturm,” De La Hoya acknowledged. “I didn’t train well, was slow. I felt like a loser. It’s a hard lesson to learn, but I learned it. . . . I need this, someone to stir something inside of me.”

While other prominent fighters go through doubts about retirement, De La Hoya, 35, said he will walk away from the sport after taking one more fight after Mayweather.

He admitted this week that while he ranks his ring success -- 10 world titles in six divisions -- “a good career . . . I’ve fought everybody there is to fight,” he also regrets leaving some of his best effort “on the table,” in going 7-5 in his last dozen fights.

“I want to beat the best pound-for-pound fighter in the world before I leave,” De La Hoya said.

That plan required a selection of former super-featherweight champion Forbes (33-5, 9 KOs) as the opponent. De La Hoya had the option of picking either unbeaten, 26-year-old welterweight Dmitriy Salita (28-0) or personable International Boxing Federation light-welterweight champion Paulie Malignaggi (24-1, 5 KOs) for this bout that could draw a capacity crowd of 27,000.

“Forbes was the toughest of the three,” Gomez said, “and Oscar said, ‘I want him.’ I asked him, ‘You sure?’ And he told me he needed a challenge, and wanted to look great.”

Forbes, runner-up on the 2006 reality television series “The Contender,” emerged because he is a protege of training by the Mayweather family, he has never been knocked down, and De La Hoya had seen him fight and was impressed.

Bruce Trampler, the Top Rank matchmaker who directed De La Hoya’s career from 1992 Olympic gold through several world titles, told Gomez this week, “This is the best thing for Oscar, and it gives him the edge against Mayweather.” Mayweather, he said, may be slowed because he will have had a 10-month layoff before the rematch.

De La Hoya spent training camp in Puerto Rico, re-energized, he said, by his reunion with trainer Floyd Mayweather Sr., who talked his way back to De La Hoya by lamenting how the rift with his son was deep and that Floyd Jr. “deserved a whuppin’.”

“I just found out how to relax in the ring [this camp], and not be tense,” De La Hoya said. “Mayweather has been telling me for years, throw my combinations, relax. I’ll have a style change in this fight. I can box on my toes and box elusively.”

And he’ll have most of the 27,000 on his side.

“The idea for doing this fight in L.A. came up a few years ago, and I had to time it perfectly with my retirement,” De La Hoya said. “The decision to do it now was a no-brainer. I had to do it, one more time at home.”

Across the ring at the first bell, De La Hoya will be looking at a fighter holding out hope his theory is rooted in reality.

“I still think I was a little bit overlooked,” Forbes said this week. “Maybe he’s put more thought into me than I believed at first . . . “

More pounds too.

At Friday’s weigh-in at Pershing Square downtown, and in front of hundreds of De La Hoya supporters, both fighters weighed in at the limit, 150 pounds. Actually, De La Hoya first weighed 150 1/2 pounds, up from that 147. The solution? The socks came off.

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lance.pugmire@latimes.com