It’s just one single “perfect punch” that Juan Manuel Marquez needed to finally defeat his arch nemesis Manny Pacquiao…

The 39-year-old Mexican boxer blasted Pacquiao with a huge right hand with just one second left in the sixth round of their highly anticipated welterweight fight on Saturday night to leave his Filipino adversary face-first on the canvas and score a decisive knockout, giving Marquez his first defeat of  Pacquiao in four attempts.

Pacquiao had charged into the Mexican counterpuncher’s danger zone and ran into a right hand, dropping the Filipino along the ropes. Pacquiao lay motionless for several seconds as the sellout crowd of 16,398 at the MGM Grand Arena erupted.

“That’s boxing,” said Pacquiao. “I started to get confident, but I never expected that punch.”

Marquez said, “I knew after the last three rounds that he was going for the knockout and I could be knocked out at any time. I hit him with the perfect punch.”

Pacquiao’s trainer, Freddie Roach, felt his fighter was in charge throughout the bout. “He just got a little too careless, but he was hurting Marquez,” he said. Pacquiao had knocked Marquez down in the fifth round and nearly had him stopped at that point.

Marquez, who’d never won a fight above 140 pounds, was behind on all three judges’ cards when the fight dramatically ended.

This time, there was no need for Marquez (55-6-1, 40 KOs) to complain about the judges’ scoring. The former four-division world champion had bitterly disputed the results of their three previous encounters, particularly his points loss last November in Las Vegas.

Asked about a fifth fight between the two, promoter Bob Arum, who handles Pacquiao, said, “Why not? We haven’t seen such an exciting fight in years. This fight will go down in history as a ring classic.”

Pacquiao (54-5-2, 38 KOs), who also went down in the third round, has lost two fights in a row for the first time in his career and was stopped for the first time in more than 13 years.

He said he would be up for a fifth fight. “It’s up to my promoter. Let’s fight again,” Pacquiao said before heading to the hospital.