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Serena Williams defeated Maria Sharapova for the 15th consecutive time Thursday, rallying in both sets to win, 6-4, 6-3, in the Sony Open semifinals in Key Biscayne, Fla. Seeking a record seventh Key Biscayne title, Williams improved to 16-2 against her favorite foil. Sharapova hasn’t beaten Williams since 2004. The top-ranked Williams hit nine aces and broke five times, which helped her rebound from deficits of 4-1 in the first set and 2-0 in the second. Her opponent in Saturday’s final will be either Li Na or Dominika Cibulkova.