Frazier emerged as the top contender in the late 1960s, defeating opponents that included Jerry Quarry, Oscar Bonavena, Buster Mathis, Eddie Machen, Doug Jones, George Chuvalo, and Jimmy Ellis en route to becoming undisputed heavyweight champion in 1970, and he followed up by defeating Ali by unanimous decision in the highly-anticipated Fight of the Century in 1971. Two years later, Frazier lost his title to George Foreman. Frazier fought on and beat Joe Bugner, lost a rematch to Ali, and beat Quarry and Ellis again.