Juan Manuel Marquez's 'perfect punch' leaves questions over Manny Pacquiao future

The genuine rivalry between Manny Pacquiao and Juan Manuel Marquez has taken eight years, four fights, two hours of boxing and a punch that travelled less than six inches to reach some type of ending.

On Saturday night at the MGM in Las Vegas, a capacity crowd fell silent for the longest and most savage of seconds when Pacquiao fell unconscious to the canvas at the end of round six.

The great Filipino, a world champion at eight weights, was out cold for over a minute and the fourth fight between the two bruised and bloody men was over.

However, as they each received medical clearance for the beating they had taken in the brutal modern classic there was already bold and sensible talk of a fifth fight. "Why not?" said Bob Arum, the promoter of the fight.

On Saturday Pacquiao cleared in excess of $26m (£16.25m) and Marquez, who won for the first time in their series of fights, left town yesterday with as much as $10m (£6.25m) in his pocket. A fifth instalment would probably make Marquez $20m (£12.5m) and it is unlikely that Pacquiao, who is already the second highest-paid sportsman in the world, would make any less than he did on Saturday.

There are few wise heads in the boxing business in the aftermath of a super-fight in the casino city, but thankfully Pacquiao's long-term trainer Freddie Roach provided a degree of sanity as the dawn approached. "We need to look at the fight and I need to look at Manny," insisted Roach. "I want to be sure he is fine and I will be able to tell. I know him." Roach is correct and Pacquiao's clean bill of health after a CT brain scan at the hospital only tells part of the story.

A good trainer will know if his fighter is "gone", which is not a medical term, but it is one that correctly ends a fighter's career if the diagnosis is made. "If I like what I see he will fight, if I don't then he will retire," promised Roach, who admits to fighting too long as a professional boxer and not taking the advice of his trainer Eddie Futch when he was told to quit.

On Saturday night Marquez was trailing on all three cards by just one point when he connected sweetly with the shortest and most deadly of rights to send Pacquiao into oblivion. Roach claimed that the punch travelled two inches and he is probably right, but Pacquiao was charging forward, his right leg off the canvas, and Marquez was leaning into the lunge and at that perfect point of impact the fist found the chin and that was it.

"I threw a perfect punch," Marquez said after the fight. "I knew Manny could knock me out at any time.

"I felt he was coming to knock me out the last three rounds, and I knew he was going to be wide open."

Pacquiao went down in the third round but returned the favor and knocked down Marquez in the fifth. The fighters were exchanging big punches throughout the sixth round before Marquez sent Pacquiao to the canvas at 2:59 of the round.

Marquez dropped a controversial decision to Pacquiao, to never fight his nemesis again.

Marquez improved to 55-6-1 with the 40th knockout of his career.

Pacquiao is 54-5-2.