Even before Manny Pacquiao went down in the sixth round of his fight with Juan Manuel Marquez, rumors of his retirement floated around the boxing world. 

It was an ugly sight seeing this world champion face down and knocked out for a while on the canvas, however, as we learn from the past, it is difficult for boxers to stay away from the ring. 

"To all my fans, I would like to thank you for your prayers and assure you that I am fine," Pacquiao said. "I am looking forward to a nice rest and then I will be back to fight," he added.

Whether it is for financial reasons or a geniuine love for the game, the greatest of greatest never know when to call quits.

From Muhammad Ali to Julio Cesar Chavez to the late Hector "Macho" Camacho, for one reason or the other, these guys were unable to leave the game and we saw them fighting way beyond their prime. 

Ali was 39, Camacho was 48 and Chavez Sr. was 43 when they participated in their last professional fights. 

Pacquiao has a career outside of boxing. He is a government official in his native Philippines as he enjoys to give back and help those in need. Many would say that Pacquiao has no reason to continue taking punishment on the ring.

However, when looking at the fight as a whole, Pacquiao was hitting hard and in control. He told Larry Merchant following the fight that he was simply overconfident. He never saw the punch thrown by Marquez because he was too caught up trying to hurt his opponent.

Pacquiao had cracked Marquez's nose and he was on the attack. Pacquiao was moving a lot and proved agile throughout the fight. Instead of becoming fatigue, he was as active moving his head and around the ring at the same speed in the sixth round as he was in the first. 

Marquez was confused, yet proved superior landing two clean overhand rights on Pacquiao's jaw. Because Pacquiao got careless, the punch proved effective twice, the second time more lethal than the first. Pacquiao is willing to go for a fifth fight if promoters are willing to make it happen. 

Though Pacquiao's career is now in question, one thing that is certain is that a fight against Floyd Mayweather Jr. is never going to happen as Pacquiao's market has sunk. 

Whether Pacquiao calls it quits or not, he will always be one of the greatest boxers to lace up some gloves.