FORT LAUDERDALE, FLA. – Floyd Mayweather has done the math, give or take a tablespoon or two, and that has left him even more baffled than he was before at the demise of his much-anticipated fight with Manny Pacquiao.

In the end that fight didn’t happen because, well…who knows, but it sure wasn’t the math.

“You got 380 tablespoons of blood in your body,’’ Mayweather said recently. “When they draw blood they draw out one tablespoon. You still got 379 tablespoons left. You lose more than a tablespoon of blood in a fight. You lose more than that from your nose and mouth. I’m not talking about me! I’m talking about them other guys (who get hit more in a fight than Mayweather has been in his 40-fight career).

“I never knew a fighter didn’t want to take a $25 million drug test. If I was all about the money (with a guy who calls himself “Money’’) like people say I would have taken the (Manny) Pacquiao fight. I just feel we should clean up sports, period. Records are being broken by cheaters.

“This should happen in all sports to separate the good athletes from the great athletes. In boxing if you start good you usually are all the way good or you start to go down with age. You don’t start off average in this sport and at 25 suddenly become great. You don’t get knocked out at 106 pounds and then come knock out bigger guys. Boxing’s not like that.

“I know I’m a clean athlete. They can come whenever and take blood or urine. Any other athlete who’s clean should do the same. If you’re not on nothing, what’s the problem? A tablespoon of blood?’’

We may never know the real problem that caused Pacquiao to refuse a guaranteed $25 million to fight Mayweather and then settle for far less to face Joshua Clottey March 13 in a fight, frankly, that pales in comparison not only to Mayweather-Pacquiao but also to what Mayweather ended up with, which is a long-awaited showdown with 38-year-old welterweight champion Shane Mosley.

That fight came about because Mosley immediately agreed to the random blood testing Mayweather demanded, insisting he welcomed the chance to prove he is not using performance enhancing drugs as he did prior to his rematch with Oscar De La Hoya. Mosley has long insisted he did not know what he was using under the direction of since deposed strength and conditioning coach Darryl Hudson and one can debate that all day and never know the answer, but one thing is clear.

Both fighters will be clean on May 1 and boxing will be the better for it because unlike baseball, track and field, football and a growing list of other sports, two of prize fighting’s biggest names have decided they won’t wait for the men who run their sport to take a step. They’ll do it themselves.

That Pacquiao refused doesn’t mean he’s guilty of anything, but in the present climate it casts a dark shadow on him because professional athletes long ago lost the presumption of innocence when it comes to PEDs. With the making of the Mosley fight, Mayweather dragged his sport a step closer to the 21st century by stepping into the ring with a guy as willing as he is to prove he’s running on regular, not high-test, a statement that sadly seems it has to be made in these chemically-fed days of sports achievement.

While that is good news for boxing, which has been maligned for so many years in so many ways as being behind the times, what is better news is that Mayweather landed the best opponent not named Manny Pacquiao that money could buy.

Of late it had become fashionable for know-nothings to claim Mayweather had been “ducking’’ Mosley when the facts were he had pursued him back in 1999 when Mosley was still undefeated. At that time Mosley chose not to face Mayweather, moving up in weight for bigger money fights, which was understandable from a business standpoint but could have opened him up to the same charge.

Yet when Mayweather was in the driver’s seat and refused to give Mosley a shot years later, after Mosley had lost several times and no longer carried the same cachet he had earlier, he was accused of avoiding Mosley. Now that, like the lingering doubts about PED use in boxing, have disappeared in this fight because the two men found themselves in a position where they needed the other and didn’t feel like fighting over the particulars. Instead they opted to take the old fashion route and fight where it counts – in the ring.

“The thing is in the sport of boxing, like life, everything is timing,’’ Mayweather (40-0, 25 KO) said. “Just like inside the squared circle. A lot of people need to realize in 1999 I was trying to make a fight with Shane Mosley when he was still undefeated. Now, five losses later, I got the bad end of the stick.

“We’re a lot older now. I don’t know what he’s got left. He looked tremendous against (Antonio) Margarito (who he stopped in nine one-sided rounds) but if I knock him out then it’s ‘He was supposed to knock him out.’ If I don’t then ‘He didn’t knock out Mosley.’ But I don’t care about the negative things people say. I’ll box. I’ll be smart. I’ll be me. I’ll break him down.

“When my career is over, fans will appreciate my skills and boxing ability. There’s nothing cool about taking punishment. What’s cool is dishing it out. I’m in a brutal sport. We’re in hand-to-hand combat. If a guy is on (steroids) I’m basically fighting a robot. It’s like putting steel in the glove.’’

The major reason Mayweather came back to boxing (short of the obvious financial windfalls) was for fights like this one. It is why he sought a match with Pacquiao, who unseated him as pound-for-pound champion after the former went into a self-imposed exile from the sport for 21 months.

Mayweather is back only to fight mega-fights. Only to face mega-challenges from fighters nearly as talented as he is. Along the way, he will make mega-money but the latter comes with the former and he knows that. What also comes with it is what really drives him.

“I missed the sport of boxing,’’ Mayweather said. “I truly did. I missed testing my ability against the best. Shane got to this position for a reason. Just because you had 40 good nights and he had 37 good nights (45 actually) and three he wasn’t (five to be frank) doesn’t mean he’s not a great fighter.

“I could have easily gone on a world tour fighting stiffs and made $200 million but it’s about testing my skills against the best fighters of my era.’’

Shane Mosley is surely that. Mosley destroyed Margarito in his last fight, a year ago, at a time when many felt it would be his demise. Instead he took apart the man who had taken apart Miguel Cotto and Kermit Cintron, revitalizing his own career and creating an opportunity to finally settle the debate between him and Mayweather over who ranks where in boxing’s bloody pecking order.

“You got two guys who are fast,’’ Mayweather said of Mosley. ‘That’s where timing comes in. Timing and inches. I know what I can do. I know a lot more is coming after this.’’

Maybe even Manny Pacquiao… but that will be up to how many tablespoons of blood are too many to lose to decide once and for all who the best fighter of this era really is. Two guys agreed to begin that debate by leaving no debate that they are clean athletes. If Manny Pacquiao ever wants to continue the discussion it will only cost him one tablespoon of blood for the chance to make his case.

The day he does, Floyd Mayweather will be waiting for him…gladly.