LAS VEGAS – If Juan Manuel Marquez finds a way to upset Floyd Mayweather, Jr. Saturday night he’ll be upsetting a lot of other fighters too.

Among the lightweight champion’s many old-school training methods is one he swears has helped him replenish lost vitamins and proteins for his past five or six fights.

Considering that he’s a 4-1 underdog to derail Mayweather’s return to boxing after a 21-month layoff if the 36-year-old Marquez wins you will very likely soon find a lot of young Mexican fighters eating raw quail eggs and drinking their own urine.

What was that, again?

Although Marquez spends time using such 21st Century training methods as sitting inside a hyperbaric chamber sucking on an oxygen mask, he is decidedly old school in some quaint areas of physical preparation.

*  He still runs up a mountain outside Mexico City at least once a week, as Julio Cesar Chavez once did, believing altitude training will improve his breathing.

*   As he runs he reaches down and throws boulders over his head, believing the act will build natural strength as he moves up from 135 pounds to the 144-pound catch weight he agreed to for the Mayweather fight.

*After his run he often stops to drink down a dozen or so raw quail eggs bought from a roadside stand.

And then there’s the twice weekly ingesting of his own urine, a training method not recommended at GNC or by the Surgeon General of the United States but one Marquez championed during the four-week 24/7 HBO special that followed the two fighters around to hype the pay-per-view event.

Although most doctors insist drinking your own urine, while not harmful unless you happen to be unfortunate enough to have an undetected urinary tract infection, is not particularly helpful, don’t try to tell that to Marquez.

“That’s where a lot of proteins and vitamins are,’’ he told HBO’s camera crew. “Why not drink them instead of wasting them?’’

Actually most of us could think of a lot of reasons to pass on them in favor of a strawberry smoothie, but if the 36-year-old winner of world titles in three different weight classes (featherweight, junior lightweight and lightweight) can somehow overcome all the physical advantages of size, weight, strength, speed and youth possessed by Mayweather there may be a lot of urine drinking going on in sports next week.

“You never know what lies ahead,’’ Marquez (50-4-1, 37 KO) said while pondering the boxing world’s view of his chances Saturday night at the MGM Grand Garden Arena. “Life is full of surprises. This is what motivates me – to prove everyone wrong.’’

Although Manny Pacquiao has of late been trying to prove unequivocally that size does not matter in boxing, when one looks at the slightly built Marquez standing next to the wider, thicker and more muscular Mayweather it makes you want to reach for a glass of something far more potent than a cup of urine to steady yourself.

Marquez has fought only twice as a lightweight and never at 144 pounds after spending nearly all of his career at the 126-pound featherweight limit. At a time when his speed and reflexes have already shown signs of slippage, giving up such a decided weight advantage to earn $2 million seems to many people foolhardy.

That Marquez does not see it that way is a measure of who he is and how he hopes to be remembered in boxing. His quest is to defeat someone once considered the best pound-for-pound fighter in the world before he chose to retire for nearly two years.

The reason behind that quest is the reason behind the urine drinking, raw egg eating, mountain running, endless sparring and obsessive, five-months of training. It is to cement his name for all time firmly in the annals of boxing history rather than looking back and finding yourself merely a footnote.

“It’s going to be a very difficult fight,’’ Marquez said. “I’m going to come in with a lot of speed like I have always done and that makes it very difficult. I’ve got to come in and bob and weave and bend and make him miss and then counter him. I have to wait for the right moments and pick my shots.

“He’s a counter puncher. He’s very fast and elusive and also a very defensive fighter so that will make it much more difficult. He’s a great fighter. He’s the best fighter but we will see what Juan Manuel is able to achieve in his eyes.’’

If he can find a way to out counter a counter puncher and out box perhaps the best defensive fighter in boxing, Juan Manuel Marquez will have achieved much. He may not revolutionize spots drinks if he wins, but he will have proven himself equal to the moment.

“This is the opportunity of a lifetime and he knows it,’’ said Marquez’s promoter Oscar De La Hoya, who lost a close fight to Mayweather himself several years ago. “He’s a smart counter puncher, a smart fighter so it’s a matter of throwing those jabs and feigning those jabs and putting three, four and five punches right behind that jab.

“When I fought Floyd my jab was the key. I have a great jab and when I used it I was unstoppable. When I stopped using it that’s when Floyd was able to win the fight. Floyd Mayweather is the best fighter on the planet and Juan knows that. He’s up for a big challenge but he’s ready and he knows that he has to put his life on the line. He’s willing to do that.’’

Apparently, he’s willing to do a lot of things.