Manny Pacquiao, considered by many the best pound-for-pound fighter in the world, is moving up in weight to fight Antonio Margarito for the vacant WBA super welterweight championship on Saturday at Cowboys Stadium in Arlington, Texas (9 p.m. ET, HBO PPV).

Already the first boxer to win world championships in seven different weight classes (from 112 to 147 pounds), Pacquiao can earn an eighth title with a victory against Margarito. The fight will take place at a catch-weight of 150 pounds.

If Pacquiao isn't unequivocally the world's greatest boxer -- Floyd Mayweather is the other claimant to the mythical pound-for-pound title -- then he's certainly the most exciting fighter today. Pacquiao is a global phenomenon who's cracked the sporting mainstream like no other Asian-born athlete in history. He was the subject of a 60 Minutes report on Sunday and named one of Time magazine's 100 most influential people last year. He sings, he acts. He was elected to Congress in the Philippines in May. It's been more than five years since he lost a fight.

After Pacquiao defended his 147-pound title against Josh Clottey last March, all eyes returned to the highly anticipated Pacquiao-Mayweather megafight. Negotiations fell apart over drug testing (again) and Margarito stepped in, leaving fans with a fight that feels like a consolation prize.

Margarito captured the WBO welterweight title in 2002 and held different versions of the belt off and on throughout the past decade. It seemed he'd emerged as boxing's newest superstar in June 2008 after a scintillating 11th-round TKO of Miguel Cotto for the WBA title, but an ill-fated defense against Shane Mosley six months later prompted a swift downfall. That's when Mosley's trainer noticed a plaster-like substance on the Mexican's hand wraps during pre-fight preparations. Margarito lost the title to the underdog Mosley and, weeks later, surrendered his license to fight in the United States for one year because of the illegal hand wraps. Margarito says he's fighting for the opportunity to redeem himself.

Pacquiao is on a streak of five victories against larger opponents: a ninth-round TKO of David Diaz for the lightweight title in June 2008; an emphatic ninth-round stoppage of Oscar De La Hoya in December 2008 that sent the Golden Boy into retirement; an awesome second-round starching of Ricky Hatton for the junior welterweight crown in May 2009; a TKO of Miguel Cotto in the most lucrative fight of 2009; and a shutout decision against an uncooperative Josh Clottey last March. With each successive outing, the Filipino seems to be getting better and better. He's not just bringing his punch up with him, but he's also absorbing opponents' shots more effectively.

Margarito is more of a plodding fighter -- slowish even by welterweight standards -- who stalks his opponent around the ring while throwing a high volume of punches. Many observers believe he's tailor-made for the speed-based assault of the ambidextrous Pacquiao, who fires punches from impossible angles and blurs the line between offense and defense so effectively. But Margarito has proved tenacious and durable throughout his career. His ability to press his natural size advantage -- an area where Cotto, Clottey and others have failed -- is the key to the Mexican's chances. The bottom line: Pacquiao has never faced anyone as big and strong as Margarito. For Pacquiao, this latest cross-divisional climb may be a step too far.

Freddie Roach, a four-time Trainer of the Year, is one of the game's best corner men whose teaming with Pacquiao is becoming one of boxing's historic fighter-trainer partnerships. Margarito has been working with Robert Garcia, one of the sport's up-and-coming trainers, having split with Javier Capetillo (the fall guy in the loaded gloves episode). Advantage, Pacquiao.

Intangibly, you have to wonder about Pacquiao's motivation, and whether the confidence from his string of recent victories can slip toward hubris. Distractions have been everywhere from Baguiao to Hollywood -- an angle that's been played heavily on HBO's 24/7 reality series -- but Pacquiao's team insists he's focused and prepared after a two-month training camp.

Oddsmaker William Hill lists Margarito as a 4-to-1 underdog.

The size differential lends some intrigue to the mismatch, but that certainly didn't stop Pacquiao from peppering De La Hoya, Cotto and Clottey with crisp combinations all night long. There's always the possibility of a lucky shot flipping the script, but Pacquiao ate Cotto's best shots last year and will be prepared to do the same Saturday night. Manny will prove too fast and too busy for Margarito to press his natural power advantage. Hand speed and volume punching will carry the day as Pacquiao stops Margarito in the later rounds. Pacquiao by 10th-round TKO.

Join the conversation about Pacquiao-Margarito on Twitter. Track the hashtag #PacMarg to see who's tweeting what about Saturday's fight.

· @TRBoxing (Top Rank Boxing)

· @hboboxing (HBO Boxing)

· @ChrisMannixSI (SI.com's Chris Mannix)

· @BryanAGraham (SI.com's Bryan Armen Graham)

· @timdalhberg (Tim Dahlberg, Associated Press boxing columnist)

· @orangerose (Gary Andrew Poole, Time contributing writer and Pacquiao's biographer)

· @GarethBOXUFC (Gareth A. Davies, Daily Telegraph boxing columnist)

· @NYPost_Willis (George Willis, New York Post boxing columnist)

· @latimespugmire (Lance Pugmire, Los Angeles Times boxing columnist)

· HBO's Jim Lampley, Max Kellerman, Emanuel Steward and Harold Lederman will be ringside for the main event and undercard.

· The referee assigned to the main event is Laurence Cole. The judges are Jurgen Langos, Glen Crocker and Oren Schellenberger.

· Fans can watch the official weigh-in online Friday afternoon (6 p.m. ET, The 101 Network/TopRank.com).

· The fourth and final episode of HBO's 24/7 Pacquiao/Margarito debuts Friday at 9:30 p.m. ET.

· HBO is re-airing all four episodes of 24/7 back-to-back on Saturday (9-11 a.m.). The first three episodes are currently available on HBO On Demand and will air back-to-back Friday at 8 p.m., preceding the finale premiere.

FIGHT WEEK SURVEY: Pacquaio or Margarito? Who should the winner fight next?

MANNIX: Margarito makes fun of Freddie Roach's Parkinson's Disease in viral video

PHOTOS: Pacquiao's Greatest Hits | Margarito's Greatest Hits | Pacquiao: Outside the Ring

GLICKSMAN: Strength coach Alex Ariza is the architect behind Pacquiao's historic ascent

MANNIX: Despite training camp distractions, Pacquiao ready for Margarito challenge

VIDEO: Preview: Pacquiao vs. Margarito | The Trainers | Margarito's trashed legacy | The Rise of Manny Pacquiao | Pacquiao the Politician | Antonio Margarito | Margarito sounds off | Pacquiao unplugged