Referee Kenny Bayless, center, sends Juan Manuel Marquez, from Mexico, right, to his corner after he knocked out Manny Pacquiao, from the Philippines, left in the sixth round of their WBO world welterweight fight Saturday, Dec. 8, 2012, in Las Vegas. (AP Photo/Eric Jamison)

Associated Press

Juan Manuel Marquez, right, knocks out Manny Pacquiao in the sixth round of their WBO world welterweight fight Saturday.

Associated Press

Manny Pacquiao, from the Philippines, lies on the canvas as referee Kenny Bayless kneels nearby after being knocked out by Juan Manuel Marquez, from Mexico, in the sixth round.

Associated Press

Referee Kenny Bayless, left, calls the fight as Juan Manuel Marquez, from Mexico, right, celebrates after he knocked out Manny Pacquiao, from the Philippines.

Associated Press

Juan Manuel Marquez celebrates his sixth-round knockout victory over Manny Pacquiao.

Associated Press

Juan Manuel Marquez, left, and Manny Pacquiao trade blows.

Associated Press

Juan Manuel Marquez, left, knocks down Manny Pacquiao in the third round.

Associated Press