LAS VEGAS -- As Manny Pacquiao and Floyd Mayweather limber up for Saturday's welterweight "fight of the century," a look at five great bouts that captured the public imagination.

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The Fight

Joe Frazier-Muhammad Ali, March 8, 1971: Known simply as "The Fight," Ali-Frazier I pitted the two undefeated heavyweight champions in the famed Madison Square Garden, New York with seemingly the whole world watching and taking sides. Frazier absorbed tremendous punishment but relentlessly outworked Ali and dropped him in the 15th round to win by unanimous decision. The fight was the first in an epic trilogy capped by the "Thrilla in Manila" on October 1, 1975 -- a back-and-forth battle that tested both men to the limit. Ali called that bout the closest thing to dying but retained his heavyweight title with a 14th-round technical knockout.