He's the son of a great champion, and for most of his career that's about all Julio Cesar Chavez Jr. was known for.

Now he's a star in his own right, headlining a big Mexican Independence Day weekend fight card just like his father used to do in his prime. Unlike his father, though, the jury is still out on just how good of a fighter Chavez Jr. really is.

That figures to change Saturday night when he takes on Sergio Martinez, the fighter generally recognized as the best middleweight in the world, in a 160-pound title fight full of intriguing possibilities. It's a big step up for the son of the great champion Julio Cesar Chavez, who still struggles with the comparisons to his father.

"I can't help that people say that stuff about me. I am the son and that is who I am," Chavez Jr. said through an interpreter. "He is my dad, but little by little I have proven myself. I have proven it in the ring. You have seen what I have done in the ring the past few fights. You can't take that away from me — my victories and my championship."

Indeed, he has looked impressive in his last few fights, particularly when he clubbed Andy Lee into submission in the seventh round of their June 16 fight in Texas. But though he's technically a middleweight champion, he's still very much a work in progress as an upper echelon fighter.

He'll face a technically superior and better tested fighter in Martinez, who has only lost once in the last 13 years and has held titles at 154 and 160 pounds. Chavez will have a decided size advantage, but to win he will have to turn the fight into the kind of brawl his father used to love.

His father sat next to him at Wednesday's final prefight press conference, where he couldn't resist taking a verbal jab at Martinez, who has been calling for Chavez Jr. to fight him the past two years.

"I think my son is ready for this," the elder Chavez said. "Martinez was talking a lot about Julio, badmouthing him. He's going to make him eat his words."

Oddsmakers don't give him a big chance of doing that, making Chavez a 2-1 underdog. But he'll have the highly respected trainer Freddie Roach — who also handles Manny Pacquaio — in his corner, and the vocal support of most of the 19,000 fans in a sold-out UNLV campus arena.

Roach has made Chavez into a more polished fighter after taking over as his trainer, but he's also admitted being frustrated by the fighter's approach to training. Chavez stood him up several times at his Hollywood gym, only to call Roach for workouts in the early morning hours.

"We've had a little bit unusual training camp," Roach said. "But we got the work in."

Chavez looked a bit drawn at the press conference as he struggles to make the 160-pound limit by Friday's weigh-in. Between fights he walks around at about 180 pounds, and Roach said he was still six pounds over the weight limit on Wednesday.

Just getting to the point where he is making a guaranteed $3 million before a big crowd is a victory in itself for Chavez, who didn't take up boxing until his late teens. He's been fighting now for eight years, but has been brought along very slowly, matched against fighters who he was sure to beat.

That's changed in recent fights, and so has Chavez. Though Martinez has been trying to get Chavez in the ring for some time now, promoter Bob Arum said it wasn't until now that he thought Chavez was far enough along to be competitive against a fighter the stature of Martinez.

Arum said Chavez reminds him some of his father, a straight ahead fighter who was relentless and wore other fighters down with shots to the body.

"He fights like his father, that's genetics," Arum said.

The elder Chavez is a Mexican boxing icon who dominated in the junior lightweight and lightweight divisions in a 22-year career in which he won 107 times against only six losses. Chavez fought all the best fighters of his era, including Pernell Whitaker, Oscar De La Hoya and Meldrick Taylor.

He also fought in the same arena Chavez Jr. is fighting in, beating Hector "Macho" Camacho almost 20 years ago to the day. At that fight, Chavez Jr. was a 6-year-old sitting ringside wearing one of his father's signature red headbands.

Arum said Chavez Jr. has suffered by always being compared to his father, especially when he was just starting out and wasn't very skilled.

"The initial attraction people had to him was he is the son of Julio Cesar Chavez," Arum said. "Then there was the big question whether he could fight at all. A lot of people diminished his capabilities."