Jab, right hand, hook to the liver. Left to the liver, left to the liver. Right hand over the top, left to the liver, hook to the head.

Right hand, hook to the liver, left uppercut, left to the liver.

From the beginning, Jose Luis Castillo looked like somebody. The way he moved, the way he went about his work expressionless and stoically. The way he appeared supremely concentrated on the task at hand, which was usually destroying the opponent’s innards and taking his heart.

The way he cut off the ring effortlessly, trapped his opponent against the ropes or in a corner, and committed to his body attack. Then, when it was all over and his opponent’s kidneys were bruised and puffy and his urine was beet-red and they were wondering why fuzzy blue unicorns were cheering from the front row,

Castillo would finally reveal that handsome-but-hardened smile.

As though taking his opponent’s will was just another day at the office.

Yes, right from the beginning, Castillo didn’t look like just anybody. He looked like somebody, and that somebody was Julio Cesar Chavez, the greatest Mexican fighter of all time. The same handsome-but-hardened smile. The same expressionless demeanor. And the same hook to the liver.

That classic, beautiful, priceless hook to the liver.

And that’s no accident.

For years, “El Temible” served as Chavez’s chief sparring partner, which speaks volumes about Castillo’s testicular fortitude. Getting in the ring, day after day, with a human buzz saw, fielding left hook after left hook to the midsection from the best pound-for-pound fighter in the world, takes guts.

But Castillo somehow ignored the pain and learned from the hellish sessions, and, as Chavez’s peerless career was coming to a conclusion, Castillo’s was taking off.

Before that, though, Castillo toiled in obscurity.

He was 18-0 before he lost his first fight, to future WBC featherweight champion Cesar Soto. He was stopped on cuts in the second round.

He lost two more times on cuts, to Javier Jauregui, and again to Miguel Alvarez. Bad luck for a fighter with so much talent, and so much toughness.

But he was learning from Chavez. Learning the combinations that he would eventually throw without thinking.

Jab, jab, right hand to the head, left to the liver.

Left uppercut to the head, right to the body, left to the liver.

After the Alvarez loss, Castillo’s luck suddenly changed. The cuts didn’t seem to be a factor anymore, and Castillo, now a 135-pounder, went 7-0 with 5 knockouts. And, he got a title shot against WBC lightweight champ Stevie Johnston.

He beat Johnston on June 17, 2000, via majority decision, in that year’s “Upset of the Year.” He did it again a few months later, also via close decision.

And that was no small feat. Johnston was one of the slickest, most skilled fighters in boxing. Castillo, the old pro, used all of those sparring sessions with the great Chavez and put it to use.

He won a world title.

He made a pair of defenses, crushing former titlist Cesar Bazan (KO 6) and Sung-Ho Yuh (KO 1). And he looked just like Chavez in the process.

Jab, right to the head, left to the head, left to the liver. Right to the head.

As Pernell Whitaker was to Chavez, though, Floyd Mayweather was to Castillo. Mayweather beat Castillo twice. Officially, anyway. The first one, in April 2002, was pretty much a rip-off. Castillo hunted Mayweather down from the opening bell, refusing to get discouraged by the speed and talent that gushed from one of the best fighters of the last generation.

Mayweather was confused, lost, as Castillo pressured him and beat on his flanks and made him wish he’d picked another lightweight to pick fight. Mayweather had his moments but, at the end of 12, the decision appeared obvious for Castillo.

Mayweather won.

“Pretty Boy” didn’t take any chances in the rematch eight months later. He stayed away and boxed. Castillo pursued, but was out-sped, and outboxed.

Back to the drawing board.

After wins over anonymous competition, and rumors that he couldn’t make 135 pounds anymore, Castillo was matched with Juan Lazcano in June 2004 for his old WBC lightweight belt, recently vacated by Mayweather. Lazcano gave Castillo a good fight for 10 rounds, but Castillo’s experience showed down the stretch.

Sonora’s pride punished Lazcano in the championship rounds, and Castillo re-won the championship.

Remarkably, he seemed to get better with age.

He beat the slick Joel Casamayor in December 2004 via decision, and then knocked out Julio Diaz in March ’05 to pick up the IBF title. That set up the fight that would immortalize him.

Diego Corrales was on a roll himself, and their May 7, 2005, matchup in Las Vegas was one of the more anticipated lightweight fights in recent memory.

We all know what happened next. Castillo and Corrales etched one another’s names in the history books in a savage war. It’s a fight that people will talk about for years. It was the fight of the year, the fight of the decade and, maybe, as some people predicted, the fight of the millennium.

The 10th round will forever be remembered as one of the greatest in boxing history. Castillo was on the short end of it, one of the few times in his career that his fans saw him staggered and hurt. But that’s what happens when you’re in the ring with another great fighter.

Now, the rematch beckons. Castillo is not like Chavez.

Chavez never was knocked out in his prime.

But Castillo is as close to Chavez as we have today.

He looks like him. He smiles like him. And, most importantly, he fights like him.

Jab, right hand, hook to the liver. Left to the liver, left to the liver. Right hand over the top, left to the liver, hook to the head.

Those combinations produce goosebumps. Watching Castillo fight is like traveling in a time machine back to 1989. They’ll be on display Saturday. Just like Chavez did against Taylor and Whitaker and Camacho and Rosario. If he wins, Castillo could end up being a legend — not bad for a fighter who spent much of his career in obscurity.

One day, he might even be compared to Chavez himself. Something that would surely produce a familiar hardened-but-handsome grin.