AND MANNY PACQUIAO CAME CRASHING DOWN...FACE DOWN

LAS VEGAS -- Juan Manuel Marquez spent nearly half of his decorated career in star-crossed pursuit of the win over his greatest rival that eluded him at every tortuous bend.

He'd lost two contested decisions to Manny Pacquiao after settling for a draw in their first fight back in 2004. Even as Marquez amassed Hall of Fame credentials over the past decade, it was Pacquiao who blossomed into a crossover superstar and global phenomenon, adding world titles at 135, 140, 147 and 154 pounds to the four divisions he'd previously conquered, winning election to Congress in the Philippines and being named one of Time magazine's 100 most influential people. It was for Marquez a doomed crusade as anger, paranoia and time encroached on the 39-year-old Mexican -- bottoming out with a split-decision loss in last year's third meeting which so many ringsiders believed Marquez won -- that would have driven lesser men into retirement's cold comfort.

Yet with one heat-seeking right hand on Saturday night, Marquez stamped a definitive conclusion on a rivalry that's spanned 42 rounds over seven years and three weight classes -- and laid waste to the white whale that had come to overshadow his accomplishments, among them seven world titles in four divisions, over two decades in the hardest game.

The savage punch, one his favored opponent confessed he never saw coming, left Pacquiao out cold face down on the canvas and ignited bedlam among the 16,348 mostly pro-Marquez fans at the MGM Grand Garden Arena. Cups and bottles of beer thrown aloft in celebration drenched onlookers. Pacquiao's wife Jinkee sprung from her seat and tried to scale the ring apron in teary-eyed despair. His assistant trainer Buboy Fernandez fought off the photographers that crowded his lifeless form. His strength coach Alex Ariza wrapped a cold towel around the fallen fighter's head to coax him back to consciousness. When he came to, after two minutes that felt like an hour, Pacquiao's eyes were glazed over and, as Ariza told it, he didn't know where he was.

For Pacquiao, boxing's first and only eight-division champion, it might be the end. It was the kind of knockout that ends a career, even if he continues to fight.

"I threw the perfect punch," Marquez said.

He sure did.

Whenever boxing asks the public to pay attention, it seldom lives up to its bluster. This is one of the few times the buildup to major fight was eclipsed by the event itself: a legitimate water-cooler moment. Before an audience that included such diverse notables as Mitt Romney, 50 Cent, Magic Johnson and Jersey Shore starlet Snooki, the longtime rivals delivered a performance of such heightened courage and character, no further statement is required.

Fight of the year? Probably. Round of the year, the scandously violent fifth? Possibly. Knockout of the year? Most definitely.

Pacquiao (54-5-2, 38 KOs) raced out of his corner when the opening bell rang -- Round 37 of the series for those keeping count -- setting a furious pace from the jump. Marquez picked up right where he left off in November 2011, operating off his back foot and circling to the left, measuring distance and keeping safely out of range of Pacquiao's power hand. Even as the taut feeling-out process yielded neither answers nor any hint of the carnage to come, it was apparent Marquez -- with his varied attack and brilliant footwork -- knows exactly how to fight Pacquiao where other opponents don't.

Early in the second round, Marquez (55-6-1, 40 KOs) appeared to be having trouble solving Pacquiao's head movement, though neither had landed a punch of significance until the southpaw connected with a hard left hook that moved the Mexican backward. The fight was on.

Pacquiao landed several punches to open the third before a hard right hand from Marquez -- set up exquisitely with a left-hand feint -- sent him crashing to the floor for the first time in a decade. The crowd exploded into hysterics. It was Pacquiao's first taste of the canvas since his flyweight days, way back during a 2003 fight with Serikzhan Yeshmagambetov.

"Manny came back after that first knockdown," Freddie Roach, Pacquiao's longtime trainer, said afterward. "He was charged, he just got a little too careless. He was hurting Marquez up until the knockout."

The already frenetic action managed to pick up in the fourth as Pacquiao looked to press the action, yet Marquez's deft footwork -- a hallmark of the rivalry -- continued to stymie and frustrate his opponent. At one point Pacquiao missed badly with a lunging left hook as Marquez ducked under and snuck out the back door. By now the Mexico City native was picking off Pacquiao's punches with his gloves and countering with surgical precision. The crowd was electrified, chanting and screaming, channeling eight years of frustration into one last, desperate chance at catharsis.

And then it all nearly came crashing down.

A straight left from Pacquiao rocked Marquez, whose glove touched the canvas while trying to keep his balance. A knockdown. The fifth surged forward at breakneck pace, with Pacquiao desperately trying to close the show, sensing Marquez -- whose seemingly fractured nose was spewing blood -- was ready to go. He wasn't.

"I knew in the last three rounds Pacquiao was going for a knockout," Marquez said through a translator at the post-fight press conference. "But I knew since I knocked him down first, I'd be able to knock him out."

The pace and fury and toe-to-toe action carried over to the sixth, as chants of "Manny! Manny!" improbably began to prevail, with Pacquiao delivering ruthless combinations targeting Marquez's nose. The Filipino, ahead 48-47 on all three scorecards, was gaining steam and confidence. Then, a split-second before the bell rang, Marquez uncoiled the defining punch of his career -- a well-timed right hand over the top that separated Pacquiao from his senses. Referee Kenny Bayless didn't even bother to count. The time was 2:59 of the sixth round.

... to the last I grapple with thee; from hell's heart I stab at thee ...

In no other sport, wrote Joyce Carol Oates of this brutal trade, can so much take place in so brief a period of time, and so irrevocably. So it is for Marquez, who no longer need settle for merely being a stylistic thorn in Pacquiao's side, the Ken Norton to Manny's Ali, the B-side of his generatation's signature rivalry. He can leave the game on his own terms or continue the hunt for bigger fish, though it's hard to imagine what challenge out there can promise this caliber of recompense and satisfaction.

"This victory is not only my victory," Marquez reflected. "This victory is for the entire country of Mexico."

Could a fifth installment follow? "Why not?" said Pacquiao, who turns 34 this month, before he was rushed to the hospital for a precautionary CAT scan. "It's a good fight. I was just starting to feel confident because I thought I got him. If they give us a chance, we'll fight again. I'm going to take a rest and then I am coming back to fight."

Roach seemed far more uncertain about the future than Top Rank CEO Bob Arum, who crowed about Pacquiao-Marquez V from the dais while awaiting the Mexican's arrival from his dressing room. No doubt the money will be there -- Pacquiao earned $26 million for Saturday's fight, while Marquez will collect $6 million plus a cut of the pay-per-view receipts -- but Roach's primary concern is for his fighter's well-being.

"Possible retirement, possible rematch," the five-time Trainer of the Year said. "I'm not sure which way we're going to go right now. It really depends upon how he feels and what he wants to do. We'll get back in the gym and if I see signs of decline, I'll tell him to retire. If I don't, I'll tell him to go on."

Whatever happens, Saturday's fight writ two truths large.

Pacquiao's long-fancied showdown with Floyd Mayweather, while still exceedingly plausible as a promotion, has been stripped of whatever significance it somehow managed to retain. And the legacy of Marquez, perhaps the most underrated fighter of his time, is at last beyond assail.

Called from SI