It was a straightforward start for Serena Williams at the U.S. Open. The world No. 1 was up 6-0 2-0 when her first round opponent Vitalia Diatchenko was forced to retire hurt. Williams is bidding to complete the "calendar slam" by winning all four grand slam titles in one year.
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The 2015 U.S. Open began with a huge upset, as last year's men's finalist Kei Nishikori lost to Benoit Paire in five sets in New York.
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Paire, ranked 41st, saved two match points in a fourth-set tiebreak. Afterward, he made new fans and signed autographs.
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A dejected Nishikori entered this year's U.S. Open at No. 4, his highest ever ranking.
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Defending champion Serena Williams needed just 30 minutes to see off Russia's Vitalia Diatchenko in the first round.
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Ana Ivanovic, the former French Open champion seeded seventh, joined Nishikori on the sidelines.
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She was ousted by 2014 Australian Open finalist Dominika Cibulkova in three sets.
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Men's No. 1 Novak Djokovic needed only 71 minutes to beat Brazil's Joao Souza.
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Djokovic is bidding to become the second man in the last 45 years -- after Roger Federer -- to play in all four major finals in one season.
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The man who beat Nishikori in last year's final, Marin Cilic, progressed in straight sets over Argentine qualifier Guido Pella.
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Venus Williams was embroiled in a slugfest, blowing match points in a second set before seeing off Monica Puig in three.
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Mardy Fish, a former top-10 player, was another winner. Fish, afflicted by a heart ailment and anxiety in recent years, is playing in his final tournament.
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