Julio Cesar Chavez Jr. is the star of the show on Saturday in San Antonio, the one who is supposed to bring in the fans, win the fight and continue his rise as a marketable commodity. John Duddy is just the opponent.

And that’s OK with the affable Irishman, who as excited about this fight as any in his seven-year career. He acknowledges that a victory for Chavez in the main event of a pay-per-view card would give his career a significant boost, one that could lead to big-money fights against high-profile opponents.

The same goes for Duddy, though. If he wins, he figures, he would reap the benefits.

“This is a tremendous opportunity for me ÔǪ pay-per-view main event, the whole world watching,” said Duddy, who has been based in New York his entire pro career. “This is what you dream about when you’re a kid. I think the winner will be knocking on the door of fighting for a title, whoever the winner is.

“I’m going to try to make the most of this opportunity.”

Duddy (29-1, 18 knockouts) quickly developed a big following in the New York area because he seemed to have it all – a knockout punch, good looks and his Irish charm. He fought at Madison Square Garden in only his 16th fight in 2006, stopping Shelby Pudwill 1:51 after the opening bell – his eighth first-round KO.

By 2008, Duddy, still undefeated, had climbed into the alphabet-soup rankings and was in the conversation for seven-figure paydays against some of the biggest names in the sport, including then middleweight-champion Kelly Pavlik.

Then Duddy’s limitations were revealed.

Two fights after the sensational Pudwill victory, he won a life-and-death decision over badly faded Yory Boy Campas and then struggled with other marginal opponents before finally losing a split decision to journeyman Billy Lyell last year, which killed any immediate talk of big-money matchups.

Duddy demonstrated that he is merely a pretty good boxer with defensive deficiencies who probably would never become an elite fighter, although he always comes to fight.

On top of that, he had an acrimonious split with handlers Eddie and Tony McLoughlin that resulted in a lawsuit, Duddy alleging they mishandled his career and violated provisions in their contract.

Duddy will probably always have his fans in New York but things certainly didn’t look good as recently as a year ago.

“A lot of things happen, like any businessman,” Duddy said. “We went certain directions; it didn’t work. I’m happy enough with what I’m doing now, though.”

Why not? Duddy, guided by new manager Craig Hamilton, hasn’t looked like the terror of old – will he ever? — but has won his three fights since he lost to Lyell, the last one by a split decision over relative unknown Michael Medina on the Manny Pacquiao-Joshua Clottey undercard in March.

And now, because he has some credibility and is beatable, he has a high-profile fight against an equally beatable opponent in Chavez (41-0-1, 30 KOs) even with Freddie Roach in his corner. Most observers see it as a competitive fight that could turn out to be very entertaining.

“I always believe my opponents are better than the arm-chair critics say they are,” Duddy said. “He has, what, 40 fights under his belt? That’s a lot of fights. I’m sure he’s under some pressure because of his father’s name no matter what he does in the ring. He’ll always be compared and criticized.

“That doesn’t have anything to do with me, though. I’m going to give him the fight of his life on (Saturday).”

Duddy also received good news about a week ago from back home in Derry, Northern Ireland.

In 1972, in the midst of the violent conflict between Catholics and Protestants, 14 people were fatally shot by British paratroopers during a civil rights march. A report at the time indicated that the victims might’ve had weapons or explosives. However, a report published on June 15 said none of the victims “posed a threat of causing death or serious injury or indeed was doing anything else that could on any view justify their shooting”.

Among the victims on “Bloody Sunday”: Jackie Duddy, a promising young boxer and the uncle of John.

“It’s very, very important,” said Duddy, who was born seven years after the tragedy. “This will help all the families involved live in peace and move forward. For the people who lived through that era, I’m sure this is a great relief.”

Perhaps this is a good time for Duddy to be taking part in the biggest fight of his life.

Michael Rosenthal can be reached at [email protected]