One is likely to take a significant step forward in his career, the other a big step backward.

Kelly Pavlik has a great deal to prove when he meets Sergio Martinez on Saturday night in Atlantic City, N.J., on HBO. THE RING middleweight champion lost his perfect record and his imposing aura when he was dominated by Bernard Hopkins in 2008 and then had to cancel fights with Paul Williams because of an infected left hand.

A victory over Martinez, particularly a convincing one, would restore much of luster Pavlik has lost.

Martinez, a well-preserved 35-year-old Argentine based in Spain, managed to enhance his reputation exponentially in two fights he failed to win, a draw against Kermit Cintron early last year and a disputed decision loss to Williams in December.

Still, he needs a victory over a big-name opponent like Pavlik – which is missing from his resume – to assume his place as one of the sport’s elite champions.

“I think Martinez has really made a name for himself,” Pavlik said. “Everyone I talk to about the fight has seen his fight with Williams. People know he’s a dangerous fighter. And when I go in there and dominate and win, I’ll be right back on track.”

That would seem to be possible. Pavlik (36-1, 32 knockouts) is the naturally bigger and stronger fighter. He has been a middleweight or heavier most of his career while Martinez moved up from 154 pounds to 160 for the Williams fight.

Pavlik also punches extremely hard, as his impressive knockout ratio indicates. He might simply prove to be too powerful for Martinez, which has been the case against most of the Youngstown, Ohio, product’s opponents.

And Pavlik seems to be as motivated as he’s ever been. He battled through the fallout after his loss to Hopkins and the career-threatening staph infection his hand. Now, with the Hopkins fight well behind him, he said he’s completely healthy and primed to pick up where he left off in the back-to-back victories over Jermain Taylor that catapulted him to stardom.

He knows what’s at stake.

“As long as I go out there ÔǪ and keep winning, that will silence all the critics,” Pavlik said.

Pavlik probably would’ve been expected to destroy his relatively unknown foe had this fight taken place before the Hopkins debacle.

However, things have changed. Pavlik went from monster to mediocre the night two years ago he was embarrassed by a 43-year-old. And he has beaten two relatively soft opponents – Marco Antonio Rubio and Miguel Espino – since the Hopkins fight.

Meanwhile, Martinez (44-2-2, 24 KOs) outclassed the capable Cintron in most eyes and opened eyes with his skill and uncommon resilience against Williams, one of the best and most-feared fighters in the world. Many believe the southpaw from Buenos Aires should be 2-0 in those fights.

In other words, one fighter is hot (Martinez) and one is not (Pavlik).

“First and foremost I think Pavlik already had his time,” Gabriel Sarmiento, Martinez’s trainer, said through a translator. “Sergio is at his best moment and Pavlik I think is going down(hill).”

We’ll know if he’s right on Saturday night.

Michael Rosenthal can be reached at [email protected]