LAS VEGAS -- After four grueling and razor-close fights between Manny Pacquiao and Juan Manuel Marquez, the demand was for, at long last, a definitive outcome in the fourth, and possibly final, fight between these great rivals.
Well, it gets no more definitive than that.
Marquez, desperate for victory after being down 0-2-1 in the legendary series, flattened Pacquiao with a flush overhand right hand with one second left in the sixth round of their welterweight fight, sending a jolt of human electricity through the sold-out crowd of 16,348 -- in a pro-Marquez house -- at the MGM Grand Garden Arena.
Pacquiao went down face-first and was out cold, and the judges, the source of so much controversy through the first three fights, were rendered pointless. Referee Kenny Bayless didn't bother to -- or need to -- count as Marquez celebrated on the ring ropes, drinking in the cheers from his Mexican fans, who chanted for him throughout the fight.
"I knew Manny could knock me out at any time," Marquez said. "I threw the perfect punch."
It was a stunning scene and certainly brought to a close Pacquiao's incredible run that saw him win world titles in a record eight weight classes, win a congressional seat in his native Philippines and become a global star. It was also probably the final nail in the coffin for the fight most have wanted to see for years but that has gone unmade: Pacquiao against pound-for-pound king Floyd Mayweather Jr.
Before the clean knockout, it had been a tremendous action fight and a fitting bout in their all-time great series, which began in 2004 and has stretched across 21 pounds, four fights and 42 rounds.
"I was careless. He's not an easy opponent," Pacquiao said. "I did my best, but that's boxing. That's sports. I thought I got him in the last couple of rounds, but I got hit by a strong punch. I never expected that punch."
Pacquiao and Marquez both said throughout the buildup to the fight that they would be aggressive, hoping to score a definitive victory, a knockout being the preference. They certainly fought like it, delivering all the action the fans could have hoped for in perhaps the best overall action fight of the series.
Pacquiao rocked Marquez in the second round, and then the fight really heated up in the third round when Marquez scored his first knockdown, dropping Pacquiao with a right hand. Pacquiao was clearly hurt and shaky but survived the final 70 seconds to make it out of the round.
"It was a good shot, but I was able to come back and take control of the fight," Pacquiao said.
Pacquiao has had problems with his calves cramping, which seemed to come up again because he was having them rubbed down after the fourth round. But in the fifth round, he was moving well and the fighters rumbled in a round of the year candidate -- maybe the most exciting round of the series.
Pacquiao (54-5-2, 38 KOs) landed a nice straight left hand, rocking Marquez (55-6-1, 40 KOs), sending him reeling and forcing him to touch his glove to the mat for a knockdown. But Marquez responded, going right at Pacquiao and hurting him with a right hand. They slugged toe-to-toe for most of the rest of the round.
"He caught me with my hand down," Marquez said. "That was an error and we corrected it."
Going into the sixth round, Pacquiao, 33, was ahead 47-46 on all three scorecards, but that wouldn't make a difference. Marquez, his nose a bloody mess -- although it was announced after the fight that is was not broken -- landed a huge right hand over a jab from Pacquiao that missed. It connected on Pacquiao's jaw and he crumpled near the ropes, face down, just feet from former Republican presidential nominee Mitt Romney and his wife, Ann, who sat ringside.
"We always work on that punch," said Marquez, 39, a four-division champion. "The change in rhythm was important. We knew he was going to come out aggressive, so we had a fight plan that was more technique. We were able to capitalize on it.
"We knew it was going to be a very difficult fight but not an impossible fight. We work strength, we work speed, and you can see the result."
"Manny came back after that first knockdown. He was in charge," said Freddie Roach, Pacquiao's trainer. "He just got a little too careless. He was hurting Marquez up until the knockout."
When Pacquiao regained his senses, he and Marquez embraced.
"You are a great fighter," Marquez told Pacquiao.
HBO will replay the fight on Saturday night (9:30 ET).
Marquez believes he had been robbed of decisions in his three previous fights with Pacquiao, a draw in a 2004 featherweight championship fight and two incredibly close wins for Pacquiao -- a split decision in a 2008 junior lightweight title fight and a majority decision in a welterweight title fight last November.
Marquez said he knew he would have to be careful and smart because Pacquiao had knocked him down four times in the previous three fights.
"We had to use our technique and skill, and we didn't allow Manny to connect as he has done," Marquez said. "I felt he was coming to knock me out the last three rounds and I know he was going to be wide open."
Even though the fight ended with a crushing knockout, there was some talk of a fifth fight.
"A fifth fight? Why not?" Top Rank promoter Bob Arum said. "Have you seen a more exciting fight in years?"
Pacquiao, who went to the hospital after the fight to be checked out, echoed his promoter.
"Why not?" Pacquiao, who earned at least $26 million, said after regaining his senses. "Yes, 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 gonna take a rest and then I am coming back to fight."
Marquez, who earned at least $6 million plus a share of the profits from a pay-per-view that likely will exceed 1 million buys, said he would think about it. A fifth fight clearly would be his most lucrative option.
"We will relax, we will talk with the family and we will see what comes," he said.
Whatever comes, he has the definitive win he so desperately wanted.