There is, as we've heard the man himself say many times, (supposedly) no blueprint to beat Floyd Mayweather.

What Mayweather means is that he's never lost as a professional, and he is 100% correct on that front. 42 have tried 43 times, and those 42 men have all failed. The closest calls were in 2002 against Jose Luis Castillo, and then in 2007 against Oscar De La Hoya.

The Castillo Attack -- pressure, pressure, and more pressure -- has been the most referenced as likely to succeed against the modern Floyd. But Mayweather has changed since then. In fact, he's changed because of that fight. In a rematch with Castillo eight months later, Mayweather more clearly won the fight, and though Castillo still had some success, it's likely no longer true that a similar game plan would be enough to beat Floyd.

Oscar believes the key to beating Floyd is the jab. De La Hoya had great success jabbing away at Mayweather in their junior middleweight fight, but then something happened: Floyd adjusted, and took it away from Oscar. There is a common misconception that Oscar just plain stopped jabbing for no particular reason, but it was the subtle tactical adjustments of Mayweather that won him that fight, and turned him into a legitimate superstar.

Robert Guerrero (31-1-1, 18 KO) is the next to try his hand at knocking off Mayweather (43-0, 26 KO), when the two meet this Saturday night on Showtime PPV, from the MGM Grand in Las Vegas. The 30-year-old Guerrero has fought his way here, with 2012 wins at welterweight over Selcuk Aydin and Andre Berto, showcasing a fearless, bruising, and sometimes plain dirty style that allowed him to stand his ground and dish out a lot of punishment in both fights. Concerns that Guerrero, who started his career at 122 pounds and first made his mark at 126, would be physically overmatched at welterweight pretty quickly faded.

Looking at him now, and looking at old photos of his weigh-ins at featherweight, it's harder to believe he ever made 126 than it is to believe he can fight at 147.

Mayweather, 36, is as always the heavy favorite, and few expect Guerrero to provide any serious challenge, let alone win. But in boxing, as in any sport, as in anything, really, there is always the chance. There's always the chance that the Cubs will win the World Series. There's always a chance that the Lions will win the Super Bowl. There's always the chance that Michael Bay will be behind an Oscar winner.

It's not a good chance, but it's a chance.

So what do we know about Robert Guerrero? Overlook the impressive-on-paper claim of "six-time world champion in four weight divisions." Here's the reality of that: Guerrero has won world titles in two weight classes, a total of three times. He beat Eric Aiken for the IBF featherweight title in 2006, then lost it in his first defense against Orlando Salido, but the result of that fight was changed to a no-contest after Salido tested positive for a banned substance.

In 2007, Guerrero beat Spend Abazi for the vacant title he technically never lost, given the no-contest ruling. He defended it twice, against Martin Honorio and Jason Litzau. In 2009, Guerrero defeated Malcolm Klassen for the IBF super featherweight title. He never defended it.

The other world titles that his PR team claim are interim belts at 135 and 147, but nobody anywhere considers an interim title a "world title reign," even with titles so diluted to the point of being pointless these days, even when we're talking "legitimate" belts (WBC, IBF, WBA, and WBO). It's a decent tagline in a press release, but Guerrero is by no honest measure a six-time world champion in four weight classes.

Now, I don't mean that to discount what Guerrero has done. Hell, the guys he beat for interim belts (Michael Katsidis and Selcuk Aydin) are arguably better than the guys he beat for "real" world titles in Aiken and Abazi. And his November defense of the interim WBC welterweight belt against Andre Berto was better than, quite frankly, the majority of "real" world title matchups you'll see yearly all over the world.

Berto was Guerrero's best win, and firmly established him as a force at 147. Andre Berto, derided by many for a criticism that is now years out of date, is an exciting, vulnerable, and talented fighter. He's not an elite-level fighter by any means, but when you get past Floyd Mayweather, Juan Manuel Marquez, and Manny Pacquiao, Guerrero and Berto are right there on par with the rest of the division's notable fighters.

But Berto is not Floyd Mayweather, as he proved with his hopeless attempt at a shoulder roll defense, which got him repeatedly smashed in the face by Guerrero. "The Ghost" won't have such an easy time against the real McCoy on Saturday, and Guerrero and his team are, of course, well aware of that.

What gives Guerrero any hope in this fight? Let's look at a few potential factors that could be keys to the massive upset.

1. Floyd Mayweather is 36, and so are his legs

The talk that Mayweather's legs are going might be brushed off by "The Money Team," but it's plain to see. This doesn't mean that Mayweather is any less an elite fighter -- he's still the best in the sport, period -- but it does mean that he's easier to hit and easier to find than he used to be. Against Miguel Cotto last May, Mayweather says he fought the way he did to put on a show, but that's bunk; Floyd was getting paid either way, and has never fought any way that suited anyone besides Floyd Mayweather. That's not a criticism. Mayweather is who he is, and doesn't fight stupid to prove a point. He's not Amir Khan or Tim Bradley.

Cotto, no spring chicken himself at the time, was able to get Mayweather on the ropes, and even Victor Ortiz had a little success in doing that in 2011. A younger version of Cotto, say a 2007 version, may have actually been able to beat last year's Mayweather. Floyd has rehired his father to semi-replace his uncle Roger after being displeased with his defensive performance last year. But if the legs just aren't there, he's never going to be the unhittable wizard he once was, no matter who coaches him, or how they do it.

2. Floyd Mayweather is a part-time fighter

Since beating Oscar De La Hoya in 2007, Mayweather has fought just five times. Though Floyd stays in immaculate condition year-round, and has never looked rusty in any fight, time will always catch up -- even Bernard Hopkins will eventually falter badly, if he doesn't retire first.

It's hard to continue to succeed on the top level when you fight once a year, but Mayweather has done it for the last five years. As he ages, that is going to become more and more difficult. So far, he's been incredibly impressive with this schedule. When will the years and the inactivity bite him?

3. Floyd Mayweather spent three months in jail last year

As for staying in immaculate condition, we should have zero fear that Mayweather will be "out of shape" on Saturday, but he may not be in the sort of shape he has been for his other recent fights. A three-month jail stint last year meant three months out of the gym, three months without real boxing workouts, and three months without an athlete's diet.

4. Robert Guerrero is desperate for this win

Here's something that isn't about Mayweather blowing a fuse physically. Guerrero is incredibly determined, and I've seen few fighters seem so desperate to win a fight. I don't mean "desperate" in a negative sense at all. This is an enormous opportunity for Guerrero. This very matchup was laughed off one year ago, when he first made the public challenge.

For Guerrero, this fight is everything. It's the culmination of all the work he's put in, all the trials and tribulations professionally, and in some respects, personally. His career was put on hold several times to deal with bigger matters. And he's here now, fighting the biggest pay-per-view draw in the business. This is his shot to not just validate himself as a top fighter of the year, but to go down in history as the man who finally beat Floyd Mayweather. And you can see it, hear it, and almost smell it every time Guerrero talks about this fight.

No one is going to argue that Guerrero has a good shot to win this fight, at least among people who aren't associated with Team Guerrero, or with promoting the event. But he's as worthy a challenger as is available given the political restraints of matchmaking today, and to argue that he's "hand-picked" is foolish and misinformed, but then that would be nothing new for Mayweather detractors. Guerrero has earned this fight as much as anyone who was actually available for the fight.

In five days, he gets his shot.