LAS VEGAS – Rocky Marciano was one of the hardest punchers in the long history of boxing, but it wasn't The Brockton Blockbuster's power that was primarily responsible for his 49-0 record.
Marciano's chin was like concrete, and he took punches better than just about any man who ever lived.
Yet, because he fought in an era largely devoid of great heavyweights, Marciano isn't as celebrated as many of the greatest fighters in history.
He's remembered as one of the best, but not the best.
Marciano's situation in the all-time rankings brings to mind the man who will try to match his famous 49-0 mark Saturday.
Floyd Mayweather will face Andre Berto in a welterweight title fight Saturday on pay-per-view at the MGM Grand Garden in what he says will be his final match. Mayweather, who frequently refers to himself as "The Best Ever," is 48-0 and is better than a 30-1 favorite to top Berto.
Whether Mayweather is the greatest fighter who ever lived, regardless of weight, is something that will never be proven and is no more than a matter of opinion.
There is little gray area for Mayweather. He has numerous detractors among today's boxing fans, who routinely rip him for dodging opponents or fighting them long after they were at their best.
His ardent supporters, of which there are equally as many, blindly view him as the greatest fighter in history, pointing only to his record and not considering competition for a moment.
The truth, of course, is somewhere between the extremes. Mayweather is one of the best fighters who's ever lived, and putting him in the top 25 of all time isn't a stretch.
Mayweather's 19-year professional career spans five weight classes. He began in 1996 as a 130-pounder, and fought as well at lightweight, super lightweight, welterweight and super welterweight.
The fewest criticisms of him came when he was a super featherweight. At 130 pounds, he defeated the classy Genaro Hernandez in 1998 to win his first world title, the WBC super featherweight championship.
Hernandez, 38-1-1 when they fought, had never previously lost at 130 pounds, but he was never competitive in their fight before it was stopped.
Among the other top super featherweights of the day that Mayweather defeated were Jesus Chavez (35-1 at the time); Carlos "Famoso" Hernandez (35-2-1); Diego Corrales (33-0); Goyo Vargas (40-6-1) and Carlos Gerena (34-2).
The two notable 130-pounders of that time he didn't face were Acelino Freitas and Joel Casamayor. Both, though, were under exclusive contract to Showtime and Mayweather at that point was tied up with HBO.
He moved to lightweight, where he fought in 2002 and 2003. He faced the man then generally regarded as the best lightweight in the world, Jose Luis Castillo, in his move up from super featherweight.
He won a unanimous, but controversial, decision in their first fight, then won a clean verdict the second time out.
Mayweather began to receive criticism for his choice of opponents in 2003, when he made title defenses against Victoriano Sosa and Phillip Ndou. Ndou, in particular, wasn't that highly regarded.
Top Rank wanted Mayweather to fight Julio Diaz at the time, but HBO insisted on Ndou after receiving media pressure favoring Ndou. He didn't face Stevie Johnston, Juan Lazcano or Freitas, who also was a lightweight by that point.
One man many wanted to see him fight in the early part of the 2000s was Shane Mosley, but that fight took years to happen. Mosley jumped from lightweight to welterweight in 2000 (to fight Oscar De La Hoya) and never went back.
There remains a dispute between the two fighters to this day over which didn't want to fight the other. Mosley said he wanted to face Mayweather at lightweight, but Mayweather declined. Mayweather said he approached Mosley, who was doing television at one of his fights in Grand Rapids, Mich., and sought a fight that Mosley rebuffed.
Mayweather moved to 140 pounds in 2004, and this is where the critics began to feast.
He fought ex-champion DeMarcus Corley in a WBC title eliminator to earn the right to fight for the belt. Corley hurt Mayweather badly in the fight, but Mayweather won 11 of the 12 rounds to take a unanimous decision.
Among the top 140-pounders in 2004 were Kostya Tszyu, Vivian Harris, Sharmba Mitchell, Miguel Cotto and Ricky Hatton.
Mayweather fought the unheralded Henry Bruseles after beating Corley, then went on in 2005 to destroy Arturo Gatti to win the WBC super lightweight belt in what was his first pay-per-view bout.
He gave up the title later that year and moved to welterweight, where he took on Mitchell in a non-title fight.
Mayweather was focused on De La Hoya, who wouldn't fight him until 2007 and then at super welterweight. But Mayweather did fight Zab Judah in 2006, who was regarded as one of the top two or three welterweights in the world at the time.
But he didn't face Mosley or Antonio Margarito in that span.
After besting Judah, he routed Carlos Baldomir, who had won all of Judah's title belts. Then came the fight with De La Hoya, which Mayweather won by split decision.
After De La Hoya, he went back down to welterweight and blew out Hatton in a fight that was never competitive. After a brief retirement, he returned to rout Juan Manuel Marquez when Marquez jumped from lightweight to welterweight to face him.
He finally met Mosley in 2010 when Mosley was nearly 39. After losing to Mayweather, Mosley never recorded another significant win. He drew with Sergio Mora, was routed by Manny Pacquiao and Canelo Alvarez, beat Pablo Cesar Cano, got stopped by Anthony Mundine and knocked out long over-the-hill Ricardo Mayorga last month.
Mayweather's record would look much better – or at least he'd take away a lot of his critics' ammunition – if he'd fought Mosley, Cotto and Pacquiao about five years earlier than he did.
But the truth is, Mayweather wouldn't be regarded as the best fighter of all time even if he'd fought them earlier.
Here is one man's opinion on how Mayweather might have fared against five members of the International Boxing Hall of Fame. If he would have run the table against them, he'd no question be considered the best.
Sugar Ray Leonard, welterweight – Leonard, 36-3-1 with 25 KOs, won world titles at welterweight, super welterweight, middleweight, super middleweight and light heavyweight.
Leonard was primarily a welterweight and a Leonard-Mayweather fight would have been best at 147.
Mayweather was a better defensive fighter than Leonard, but not by much. Leonard, though, was a far better offensive fighter than Mayweather. Leonard had a good chin and a powerful shot.
He had the hand speed to contend with Mayweather, as well as the lateral movement.
Leonard was a merciless killer when he hurt an opponent, and the hunch here is that a prime Leonard would have taken out Mayweather late in what would have been a fascinating tactical fight.
Leonard tended to punch wide at times and Mayweather's lead right hand and check hook would have given him some offense.
But Leonard's chin was quality, and he probably would have been able to withstand Mayweather's best and continue to punch.
Thomas Hearns, super welterweight – Hearns was 61-5-1 with 48 KOs and held world titles in the same divisions as Leonard: Welterweight, super welterweight, middleweight, super middleweight and light heavyweight.
He was voted by Ring Magazine in 1994 as the greatest super welterweight ever, so let's pair him with Mayweather at 154.
Of all the hypothetical matchups on this list, Hearns is the most formidable for Mayweather because of his reach. Hearns is 6-foot-1 with a 78-inch reach, while Mayweather is 5-8 with a 72-inch reach.
As Hearns showed in the first fight with Sugar Ray Leonard, he could do great damage with his jab from a distance.
Mayweather would have had to find a way to slip the jab and get on the inside, where he could take Hearns' reach away from him. But that was a risky proposition because Hearns had a devastating right. He also had a sneaky good right uppercut.
Mayweather never fought anyone quite like Hearns – few ever have, because not many of his ilk existed – and I think Hearns would have come out on top because of his reach and power.
Alexis Arguello, super featherweight –
Arguello was 77-8 with 62 KOs and is best known for his battles with Aaron Pryor at 140 pounds.
But his best weight was at 130 and that would have been an amazing fight with Mayweather.
In its poll of the best boxers of the 20th century, a panel of Associated Press experts picked Arguello as the best 130-pounder of all time.
Arguello was taller than Mayweather, though each had a 72-inch reach. Arguello bested a slew of great fighters in his era, but I suspect he would have had trouble catching Mayweather cleanly.
This would have been an amazingly compelling match with each man possessing distinct advantages, but Mayweather's defense, consistency and conditioning likely would have had him prevailing in this.
Julio Cesar Chavez Sr., super featherweight – Chavez was 107-6-2 with 86 KOs and began his career by winning his first 87 fights.
Chavez's perfect record was spoiled when he drew with Pernell Whitaker in a 1993 bout that just about everyone who saw it except for the judges and Chavez's most ardent fans felt Whitaker won.
The same things that troubled Chavez about Whitaker, his hand and foot speed, his movement and the awkward angle from which he threw his shots, would have troubled him against Mayweather.
But a fight between Chavez and Mayweather would have been fascinating at 130. Meldrick Taylor mostly dominated Chavez in a 140-pound bout, but wore down and was stopped as the bell counted down in the final round.
Given how much speed troubled him, going to say that Mayweather probably would have come out on top, though if they fought 100 times, it might have been 51-49 in Mayweather's favor.
Roberto Duran, lightweight – Duran was 103-16 with 70 KOs and is widely regarded as the greatest lightweight ever.
He was a small man who stood only 5-7 with just a 66-inch reach, but he gave the great Marvelous Marvin Hagler a scare at middleweight.
He was as tough and as ferocious as they ever came.
Mayweather might have had a shot to hold him off if they'd fought at welterweight, but the lightweight version of Duran would have bulldozed him. He was a sharp, accurate puncher with both hands who relentlessly pressured.
Duran could get lazy at times, but that was mostly after he'd left the lightweight division.
This would have been an extremely tough match for Mayweather and I believe there is a high probability Duran would have stopped him.
There are other great fighters we could have matched Mayweather against – Sugar Ray Robinson, Barney Ross, Aaron Pryor, Emile Griffith, Jose Napoles and Henry Armstrong – but the five men listed presented a great cross section of opponents who spanned the spectrum of Mayweather's weight classes.
He would have won some and lost some, which proves how great he is. It also proves that his 48-0 record is essentially meaningless in placing him in perspective all time.
However you see it, there is little doubt that Mayweather is among the best boxers who ever lived.
He's not as great as he thinks he is, but he's not as bad as many of his critics make him out to be.
He's an elite fighter who will justifiably be inducted into the Hall of Fame the first time he's eligible.