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.
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.
Paire, ranked 41st, saved two match points in a fourth-set tiebreak. Afterward, he made new fans and signed autographs.
A dejected Nishikori entered this year's U.S. Open at No. 4, his highest ever ranking.
Defending champion Serena Williams needed just 30 minutes to see off Russia's Vitalia Diatchenko in the first round.
Ana Ivanovic, the former French Open champion seeded seventh, joined Nishikori on the sidelines.
She was ousted by 2014 Australian Open finalist Dominika Cibulkova in three sets.
Men's No. 1 Novak Djokovic needed only 71 minutes to beat Brazil's Joao Souza.
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.
The man who beat Nishikori in last year's final, Marin Cilic, progressed in straight sets over Argentine qualifier Guido Pella.
Venus Williams was embroiled in a slugfest, blowing match points in a second set before seeing off Monica Puig in three.
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.