Dec 14, 2012 06:55 Marquez KOs Pacquiao in 6 Marquez KOs Pacquiao in 6 Juan Manuel Marquez, from Mexico, right, celebrates after knocking out Manny Pacquiao, from the Philippines, lower left, in the sixth round of their WBO world welterweight fight Saturday, Dec. 8, 2012, in Las Vegas. Referee Kenny Bayless tends to Pacquiao. (AP Photo/Eric Jamison) The Associated Press Dec. 14, 2012 Comments LAS VEGAS — Juan Manuel Marquez knocked Manny Pacquiao out cold with a vicious right hand at the end of the sixth round Saturday night, putting a ferocious end to the fourth fight between the two boxers. Pacquiao had been down in the third round but knocked Marquez down in the fifth and the two were exchanging heavy blows in the sixth round before Marquez threw a right hand that flattened Pacquiao face down on the canvas at 2:59 of the sixth round. The referee waved the fight to an end as Marquez celebrated and the sold-out crowd at the MGM erupted. Pacquiao was down for about two minutes before his handlers managed to get him up.