Floyd Mayweather has held dual roles for eight years as boxing's biggest draw and its best pound-for-pound fighter in the world.
But it's very possible he'll be facing the most difficult test of his career when he meets Manny Pacquiao in their long-awaited welterweight superfight on May 2 at the MGM Grand in Las Vegas.
Mayweather (47-0, 26 KOs), 38, has recorded many memorable victories against some of the top fighters of his era throughout his unbeaten run to the Pacquiao fight. Here is a countdown of the five most important wins of his career:
5. Sept. 14, 2013: MD12 Canelo Alvarez -- MGM Grand Garden Arena, Las Vegas
With judge C.J. Ross' absurd 114-114 scorecard notwithstanding, this fight remains one of Mayweather's most flawless boxing exhibitions against the 22-year-old Alvarez. It also cemented the fact that Mayweather still hadn't lost a step despite turning 36 and fighting for the second time in a calendar year for the first since 2007.
This junior middleweight title unification bout -- contested at a catchweight of 152 pounds -- still holds the record as the highest-grossing pay-per-view fight in history and generated the second-most buys at 2.2 million. But Mayweather quickly turned it into a snoozefest by repeatedly standing directly in front of the heavier puncher and making him look foolish.
In a fight many felt Mayweather would avoid because of the size difference between the two fighters, "Money" showcased his wizardry without showing an ounce of vulnerability.
4. April 20, 2002: UD12 Jose Luis Castillo (1st fight) -- MGM Grand Garden Arena, Las Vegas
After eight defenses of his junior lightweight title, Mayweather officially moved up in weight to challenge for Castillo's 135-pound belt. What happened next is dependent on whom you believe won the fight.
One thing is for certain: The rugged Castillo gave Mayweather the most difficult test of his career to date by cutting off the ring with constant pressure, particularly to the body. But despite being outlanded 203 to 157, according to CompuBox, Mayweather proved his toughness by overcoming a left shoulder injury to stand and trade at times with Castillo, landing the cleaner shots.
Mayweather found himself in compromising positions against a relentless fighter who was able to dictate the pace and distance of the fight for lengthy stretches. But he never buckled mentally or physically in what proved to be an indispensable test of his intangibles.
Mayweather went on to quiet critics eight months later by winning a decision in the rematch that was closer on the scorecards, yet far more convincing.
3. May 5, 2012: UD12 Miguel Cotto -- MGM Grand Garden Arena, Las Vegas
It may have come five years after it would have been ideal, but Mayweather-Cotto still ended up delivering periods of drama in what became a wide, yet very competitive victory for the pound-for-pound king.
Cotto boxed above the level of expectations, forcing Mayweather to dig deeper than usual to make his patented mid-fight adjustment. He also bloodied Floyd's nose in the process by tagging him with flush shots. But Mayweather, who claimed Cotto's title in his second appearance at 154 pounds, pulled away so convincingly in the late rounds that he appeared to on the verge of stopping Cotto after staggering him with uppercuts. Mayweather also showcased his unflappable nature by staying mentally focused despite a looming prison sentence (he went on to serve two months after pleading guilty to domestic violence charges).
It's a standout victory on Mayweather's resume that looks even better now after Cotto went on to win the lineal middleweight title in 2014 by stopping Sergio Martinez.
2. May 5, 2007: SD12 Oscar De La Hoya -- MGM Grand Garden Arena -- Las Vegas
Called by some "the fight to save boxing" in the lead-up, De La Hoya-Mayweather failed to live up to its lofty expectations despite generating a record of 2.45 million PPV buys that still stands. The junior middleweight title bout was tactical and competitive, yet far from memorable as De La Hoya faded late amid Mayweather's mounting attack of clean counter shots and lead right hands.
But the victory had a far greater impact on Mayweather's legacy. Already the best boxer in the world, this fight was the launching point for Floyd to become the sport's biggest (and wealthiest) personality. For a fighter who went on to become known almost as much for the record-breaking sums of money he has earned than for his unbeaten mark, the importance of this victory is incalculable.
Mayweather cultivated his villainous persona during the inaugural version of the prefight "24/7" documentary series on HBO in a way that was almost as brilliant as the manner in which he disarmed the much larger De La Hoya in the ring.
1. Jan. 20, 2001: TKO10 Diego Corrales -- MGM Grand Garden Arena, Las Vegas
If the victory over De La Hoya was the fight that effectively made Mayweather from a commercial standpoint, his brilliant dismantling of then-unbeaten Corrales in their much-anticipated showdown was his coming-out party from a critical sense.
This was the last time in which Mayweather, who was making the sixth defense of his junior lightweight title, entered the ring without being a prohibitive favorite. To many, he was the underdog because Corrales, freakishly tall for the division, doubled as one of the sport's biggest punchers.
But Floyd was too quick and far too slick, scoring five knockdowns before Corrales' corner stopped the bout. Mayweather leaped up the pound-for-pound rankings with the win and has never looked back since.