Mayweather is undefeated over his career and is the top pound-for-pound boxer in the world, according subjective sources such as Ring Magazine and computer ratings such as those found at boxing database site BoxRec.com. Pacquiao ranks third on both lists, but it’s a distant third. By BoxRec’s ratings — which are constructed according to a philosophy similar to the Elo ratings we use to rank NFL teams — the difference between No. 1 Mayweather and No. 3 Pacquiao (680 rating points) is the same as the difference between Pacquiao and No. 29 Kubrat Pulev.
For fighters at the level of Mayweather and Pacquiao, a 680-point difference translates to a lopsided matchup. Using the careers of fighters in BoxRec’s current pound-for-pound top 25, for instance, cases in which one boxer had a pre-fight rating advantage between 550 and 800 points saw the favorite win 30 times in 33 tries, good for a 91 percent success rate. (If you want a second opinion, the boxing simulation program Title Bout forecasts a Mayweather win about 70 percent of the time.)
So, if nothing changes between now and the May 2 date Mayweather suggested for his bout with Pacquiao, it’s unlikely the battle will live up to the hype.
Neil Paine on why the Mayweather-Pacquiao fight that looks like it will finally happen is years too late.
No doubt, anyone who knows anything about boxing knows Mayweather is one of the most skilled boxers of all-time, with historically great defense, speed, and tactical acumen. But it's also true that he has rarely stepped into the ring with fighters at the peak of their powers, challengers that threatened him in any real way. Some of that isn't his fault; you can only fight the contenders available to you at any point in time, and at points in his career that list was a sorry lineup. However, Mayweather has also “ducked” some of the best contenders when they were at their primes, only agreeing to fights with them either when they were too green or on the down slope. That's also a form of good defense, though not the ones the fans wanted to see. It reflects in the eye test, too. Mayweather has almost always been a PPV buy that many boxing fans have regretted because his fights are often dull marathons of dominant defense peppered with occasional precision scoring on offense.
Look at the BoxRec.com ratings for Mayweather and each of his opponents before and after each of the fights in his career: rarely has he been threatened, and the few occasions he was out-rated going into a fight were anomalous, like 2009 fight against Juan Manuel Marquez when his rating was low from a near two year layoff.
Mayweather likely retires with a perfect record, something that seems to mean as much to him as money, but in the heyday of boxing, we had the acknowledged greatest fighters of their day, like Ali and Frazier, confronting each other repeatedly, and those fights still hold court in boxing fans' memories in a way that no Mayweather fight ever will.