Serbia's Novak Djokovic has won the Australian Open six times — in 2008, 2011, 2012, 2013 and 2015, and then on Sunday. William West/AFP/Getty Images hide caption

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Serena Williams returns a shot to Venus Williams during Tuesday's quarterfinals match of the 2015 U.S. Open in New York City. Matthew Stockman/Getty Images hide caption

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Serena Williams en route to winning the Western & Southern Open in Cincinnati on Sunday. Tannen Maury/EPA/Landov hide caption

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What If Serena Williams Had Faced Tougher Rivals?
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Serena Williams serves the ball to Andrea Hlavackova during the first round of the French Open in Paris. Christophe Ena/AP hide caption

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For Sports Immortality, The 3rd Or 4th Time's The Charm
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Stanislas Wawrinka of Switzerland kisses the Australian Open trophy during the awarding ceremony after winning the men's singles final against Spain's Rafael Nadal on Sunday in Melbourne, Australia. Xu Yanyan/Xinhua/Landov hide caption

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