Former five-division champion Floyd Mayweather Jr. is fighting WBC welterweight champion Victor Ortiz on Saturday at the MGM Grand Garden Arena in Las Vegas (9 p.m. ET, HBO PPV, $59.95).

The 34-year-old Mayweather (41-0, 25 KOs) is widely regarded as one of the two best pound-for-pound fighters in the world (along with fellow 147-pounder Manny Pacquiao). The 24-year-old Ortiz (29-2-2, 22 K0s) is lesser-known among casual fans, but considered one of the sport's hottest fighters after outpointing Andre Berto for the welterweight title in a Fight of the Year candidate on April 16.

In addition to HBO's Pay-Per-View telecast, the fight is being shown in HD at nearly 400 movie theaters across the United States.

With six world titles in five divisions ranging from junior lightweight to super welterweight, Mayweather is one of the most accomplished boxers of his generation. But it's been 16 months since his last outing, and he's fought a total of 24 rounds since a 2007 knockout of Ricky Hatton. He's been far more active in the legal arena, where pending litigation against him includes four felony charges, two misdemeanors and a defamation suit. For years Mayweather has embraced the villain role. He knows people pay to see him lose. "They're all fans," he says. "They all pay." And how: Mayweather has generated 6.9 million buys in his seven pay-per-view fights, representing $375 million in revenue. Those numbers mean at least as much as 41-0 with 25 knockouts.

Ortiz has just one win over a world-class opponent in his prime: his unanimous-decision win over Berto for the welterweight title. But he has enough quick knockouts over recognizable names -- Vivian Harris (KO 3), Mike Arnaoutis (TKO 2), Jeffrey Resto (KO 2) -- to show he's more than a carefully matched prospect. Perhaps the biggest trial of Ortiz's career came when he quit during the sixth round of a 2009 slugfest with Marcos Maidana, opening himself to harsh criticism and questions about his constitution. Not until the Berto fight, where he showed tremedous courage by twice coming off the canvas to win, did Ortiz fully redeem himself.

It's difficult to pick against Floyd in any fight that can be made today, not just because he's undefeated, but because he's never been in trouble in any of his pro outings. When Mayweather tucks his chin behind his shoulder, he becomes difficult (if not impossible) to hit flush. The long layoff could affect his timing, but he was away for nearly two years before the Juan Manuel Marquez fight and didn't miss a beat. Mayweather may just be the uncommon fighter who trains every day even when there's no fight on the horizon and keeps in fighting shape.

Ortiz is a decade younger than Mayweather. He's been marketed as naturally bigger, stronger and more powerful. Critics say he is too raw and too inexperienced to contend with one of the most skilled boxers in recent memory, but he has a style that could give Mayweather trouble. Ortiz promises to be the aggressor, to apply pressure and bull his way inside. If Floyd can keep Ortiz on the outside using speed and ring intelligence, he should be able to dominate the action.

Ortiz is a dangerous puncher -- his handlers claim he's knocked every one of his professional opponents to the canvas -- but he's no stranger to the deck himself. If Berto was fast and powerful enough to put Ortiz down twice, it's hard to imagine Mayweather missing the opportunities that are sure to be there. Floyd must be careful to place his punches at his own pace and resist the temptation to be drawn into a shootout.

Oddsmaker William Hill lists Mayweather as a 1-to-8 favorite, while Ortiz is a 9-to-2 underdog.

It's been nearly 10 years since Mayweather fought a competitive young opponent. And there's plenty of reason to believe a southpaw pressure fighter like Ortiz is capable of making life difficult for him. But if Ortiz couldn't handle Lamont Peterson's speed and resistance when they fought to a listless draw nine months ago, what hope does he have against an opponent of Floyd's extraordinary skill and experience? Mayweather will allow Ortiz to tire himself out early before pot-shotting him to pieces in the later rounds and coasting to a comfortable points victory. Mayweather by unanimous decision.

Join the conversation about Mayweather-Ortiz on Twitter. Track the hashtag #StarPower to see who's tweeting what about Saturday's fight.

· @FloydMayweather (Mayweather)

· @VICIOUSortiz (Ortiz)

· @GoldenBoyBoxing (Golden Boy Promotions)

· @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)

· @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)

· @kieranmulvaney (Kieran Mulvaney, Reuters and ESPN boxing columnist)

· @AmyZopfi (Amy Zopfi, Event Services Manager at MGM Grand Garden Arena)

· @mgmgrand (MGM Grand Hotel)

· Saul "Canelo" Alvarez vs. Alfonso Gomez, 12 rounds, for Alvarez's WBC junior middleweight title (from Los Angeles)

· Erik Morales vs. Pablo Cesar Cano, 12 rounds, for vacant WBC junior welterweight title

· Jessie Vargas vs. Josesito Lopez, 10 rounds, junior welterweights

· Non-PPV bouts: Kyrone Butler vs. Cassius Clay, 4 rounds, junior lightweights; Said Ouali vs. Carson Jones, 10 rounds, welterweights; Marco Antonio Periban vs. Dhafir Smith, 8 rounds, super middleweights; Anthony Crolla vs. Juan Manuel Montiel, 8 rounds, lightweights; Dion Savage vs. Adonis Stevenson, 6 rounds, middleweights

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

· The referee assigned to the main event is Joe Cortez, a recent inductee to the International Boxing Hall of Fame. The judges are Nevada veterans Adalaide Byrd, Glenn Trowbridge, and Jerry Roth.

· Fans can watch the official weigh-ins Friday at 6 p.m. ET/PT on SI.com.

· The fourth and final episode of 24/7 Mayweather/Ortiz debuts Friday (9 p.m. ET/PT, HBO). If you missed the first three installments, they're airing back-to-back starting at 7:30. The series is also available on HBO On Demand.

MANNIX: Specter of Pacquiao looms over Mayweather-Ortiz showdown

COUNTERPUNCH: Ortiz deflects Floyd's verbal jab | Watch final Mayweather-Ortiz presser | Floyd appears on Conan

INSIDE SI PODCAST: Mannix breaks down Mayweather-Ortiz

GALLERY: Celebrities predict Mayweather-Ortiz