It's a big fight for fight fans.

Though the casual boxing follower might struggle to pick Terence Crawford or Viktor Postol from a lineup, those who label themselves as hardcore watchers will be salivating come Saturday.

The unbeaten 140-pounders -- each 28-0, with a combined 32 knockouts -- will risk their WBO and WBC championship belts, respectively, in a unification bout that headlines an HBO pay-per-view show from the MGM Grand in Las Vegas.

Postol is making the first defense of a vacant title he won with a surprising stoppage of Lucas Matthysse last fall in suburban Los Angeles. He's making his fourth ring appearance with trainer Freddie Roach, a former fighter who's risen to corner prominence through his work with Manny Pacquiao.

Crawford, meanwhile, is making his third defense of his second weight-class crown after a year-long run as the WBO's champion at 135 pounds. He was the Boxing Writers Association of America's fighter of the year in 2014 and is slotted sixth in Ring Magazine's latest pound-for-pound rankings.

It's his first pay-per-view starring role, and many expect -- particularly if he wins impressively -- that he'll be tapped as Pacquiao's foil for the seven-division champion's scheduled Nov. 5 comeback fight.

Crawford insists his focus is on his Ukrainian present, not a Filipino future, though he does acknowledge an opportunity to springboard into something larger.

"I am not thinking about (a Pacquiao) fight right now or whether I may be fighting him or if I put on a good show. My main focus is Viktor Postol," he said. "This is a very big fight for me at a very critical time of my career. This fight can take me to that next level beyond the level that I'm on right now. This fight means a lot and I do look at it as the biggest fight of my career to date."

Crawford, Pacquiao and Postol are all promoted by Top Rank, which would make for simple negotiations going forward. Postol could also get a Pacquiao shot if he wins, or such a result may prompt Pacquiao to pursue WBO welterweight champion Jessie Vargas, another Top Rank client.

Bob Arum, Top Rank's founder and CEO, began talking up the prospect of a Crawford-Pacquiao two years ago, following Crawford's lightweight defeat of Yuriorkis Gamboa.

"Down the road -- and it's very possible -- that a year from now we put him in with Pacquiao," Arum said. "That would be a huge fight and a great fight. If you really think you have a great fighter with superstar qualities, you move him that way; you don't protect him. You move a superstar into the biggest fights you can make for him, and that's what we are going to do."

And following Crawford's most recent fight, a fifth-round TKO of Hank Lundy in February, HBO analyst Roy Jones Jr. suggested -- contrary to chatter from Roach -- that he was up for the challenge.

"Terence Crawford is ready for anybody in the world, in any weight class right now," Jones said.

"For him to say he's not ready for Manny Pacquiao, I think that's very wrong. To me, Terence Crawford is ready for anybody on the planet that's close to his weight class."

The Crawford-Postol main event will top a four-bout HBO PPV card that will go live at 9 p.m. ET.

Preceding them on the broadcast is a 10-round light heavyweight bout between unbeaten Oleksandr Gvozdyk and three-time world title challenger Tommy Karpency, a 10-rounder between welterweights Jose Benavidez Jr. and Francisco Santana and bout for the vacant WBO featherweight title matching No. 1 contender Oscar Valdez and No. 2 Matias Rueda.

Crawford is a solid favorite, according to the numbers guys at Bovada.lv. It'll take a $650 wager to return $100 on him, while a $100 outlay on Postol would return $425 for an upset.

HBO PPV main card
FavoriteChallengerWeightclass
Terence Crawford (-600)Viktor Postol (+400)Junior welterweight
Oleksandr Gvozdyk (-1400)Tommy Karpency (+750)Light heavyweight
Jose Benavidez Jr. (-400)Francisco Santana (+300)Welterweight
Oscar Valdez (-2500)Matias Rueda (+1000)Featherweight

How does Crawford win?

The fight represents a step up in significance for the unbeaten Nebraskan, but whether it's a clear step up in opposition isn't so easy to determine before the opening bell. Crawford has used a switch-hitting style to defeat a series of champions and highly-regarded contenders, changing gears in the middle of fights once he diagnoses the most advantageous approach. He's shown a more aggressive offensive streak in his most recent outings, which could yield spectacular results against Postol.

How does Postol win?

He was considered a speed bump for Matthysse heading into their fight last October, but instead drove the rugged Argentine into retirement with a style that was far less robotic than many had anticipated. He'll need to bring every tool in his toolbox to the ring against Crawford, and it's essential that he establishes the fight's pace while landing power shots that make the unbeaten WBO champion a little less bold. If he can hurt Crawford, he can change the dynamics quickly.

Prediction: Crawford by ninth-round TKO.

A pick in this one largely depends on your opinion of either guy. Those who view Crawford as a potential pound-for-pound kingpin will see his versatility as the deciding factor, while those who view Postol as far more than a one-hit wonder may anticipate him using his natural size advantage to control the space and establish the fight's narrative. The guess here is more former than latter, so the expectation is that Crawford will be the faster and more skilled combatant and able to gradually wear his man down.