He’s already gone farther than he ever expected but David Diaz sees no reason to stop his forward progress now. That job will belong to Humberto Sosa, the WBC junior lightweight champion with whom Diaz will tussle with Saturday night over the vacant WBC lightweight title, and it will not be an easy one.

The reason for this is not that Diaz is the most talented fighter in boxing because he would be the first to tell you he is not, but he may be the one who best understands himself. He understands his strengths and his weaknesses, his limitations and his abilities. Most of all, he understands how to win, or at least what he has to do to win.

That self-knowledge has brought Diaz farther than he ever anticipated after failing to medal in the 1996 Olympics in Atlanta. That, actually, had been his only goal in boxing. To become an Olympian would have been enough so once he’d reached that goal Diaz was stymied for a while by a lack of focus and family problems that kept him away from boxing at one time for several years.

When he came back it was with one expectation. Boxing would be his job until it wasn’t any more. But instead of a job it became a journey, one that led him to the lightweight championship of the world on the night he cold cocked highly regarded Jose Armando Santa Cruz to lay claim to the WBC title in a fight where for a long time it looked like nothing was going to go right for him.

In the end it did because he persevered and he went on from there to defeat Erik Morales as well before finally being stopped nearly two years ago by the man who will fight the main event at Cowboys Stadium Saturday night – Manny Pacquiao. Diaz took a dreadful beating that evening but he displayed to the world the one thing he has in abundance – a heart that does not pump kool-aid.

“I just took that loss as these things happen in boxing,’’ said Diaz, who was badly cut and bruised before finally being driven onto his back by a barrage of punches there was no reason he should have been allowed to take. “It was just that type of fight. To be honest with you, the next day I was perfectly fine. I swear to you. The only thing that was really, really hurting me was my ego but I always said I rather go out on my back than quit.

“After I saw the way he beat (Oscar) De La Hoya and (Ricky) Hatton, I figure I did better than they did and they were supposed to be the crème de la crème of boxing. I gave it the old college try. I did OK. I didn’t do great but I did OK, considering my level of ability.’’

Imagine another world class athlete, which Diaz is, saying such a thing. His understanding of his limitations and his strengths, and his acceptance of both, works to his advantage not against it because while he believes in himself he knows the kind of fighter he is and the kind he is not.

For a time it appeared he would become the retired kind, a boxer whose achievements had eclipsed the talent God gave him. He had reached his goal, the Olympics, and his dream, a world championship, so maybe it was just time to move on. Diaz thought about that but in the end he is what he is. He’s a fighter and still glad to be one.

“I think I can still compete at this level another two years,’’ said the 33-year-old Diaz (35-2-1, 17 KO) this week from Dallas. “I still feel good. Everyone was saying I should retire after the Pacquiao fight but they don’t understand. I fought a special guy that night.

“He was just so effin’ fast! My God! The speed was just incredible. I’d see a punch coming and block it and get hit by three or four I didn’t see. It was my first, you could say, dramatic loss but it wasn’t like I was getting a lot of those kinds of beatings. If I was, I’d be the first to admit it. But I wasn’t so I kept working (despite a knee injury that set him back for a time) and this opportunity came along.

“It’s a good opportunity against Soto. I didn’t expect it. I thought it would take me at least a year to get another title shot but it is here. This is what you box for – to take this kind of risk.’’

Soto (50-7-2, 32 KO) previously held the WBC featherweight and super featherweight titles, leaving the latter behind to accept a shot at the 135-pound championship against Diaz and he is a formidable opponent. Tall for a junior lightweight, Soto stands 5-foot-7 ½ inches and has a 72-inch reach, a three-inch edge over Diaz. Opponents with an edge are nothing new to him however and so he is philosophical about Soto’s apparent physical advantages, just as he is about the beating he took from Pacquiao a year and a half ago.

To him, it’s all part of the life he chose. Or the life that chose him.

“My career has been a lot more than I expected,’’ Diaz admitted. “I thought being in the Olympics would be my plateau. I thought that was all I wanted to do in boxing because I didn’t medal. But I took a chance and turned pro. As a kid I couldn’t go play baseball or soccer. My Dad told me I had to do one thing or nothing.

“My football career ended when I asked him to sign the waiver so I could play in high school. He said, ‘Are you crazy? That sport is for animals!’ I said, ‘Dad, you have me boxing!’ He wouldn’t sign though so here we are.’’

Saturday night he’ll be inside Cowboys Stadium with a crowd of around 45,000 roaring in anticipation of Pacquiao’s main event against Joshua Clottey. But for a time David Diaz will be in that ring with Humberto Soto and the crowd can be sure of one thing. Diaz will give them all he has, which may just be enough for someone to give him another world title.

“I was just starting to work out again in the gym but I wasn’t preparing for a fight when they called,’’ Diaz said. “It was on Feb. 11 that I heard about it so I had about a month to train. You’d like more but when you get the opportunity you have to take it.

“It’s a lot different opportunity this time because it’s for a second world championship. I never thought I’d be a champion. It would be something to be a two-time champion, wouldn’t it?’’

Yes it would but regardless of what happens against Soto, David Diaz already is a champion and has been just about every day he’s woken up. He doesn’t need a plastic belt around his waist to prove it. The life he’s lived already does.