RIO DE JANEIRO — Top seed Novak Djokovic faces a hazardous first round at the Rio Olympics after Thursday's draw pitted him against Argentine powerhouse Juan Martin del Potro, the man who denied him a medal four years ago in London.
The 29-year-old Serb, beaten by Del Potro in the bronze medal match at the 2012 Games, is bidding to become only the third man to win all four Grand Slam singles titles, the Davis Cup and Olympic gold, after Andre Agassi and Rafael Nadal.
Second seed Andy Murray, the defending champion who will carry Britain's flag at the opening ceremony Friday, takes on Djokovic's Serbian teammate Viktor Troicki in round one while defending women's champion Serena Williams opens her campaign against Australian Daria Gavrilova.
Williams is going for a fifth Olympic gold medal, as is her sister Venus who plays Kirsten Flipkens in the first round.
Venus will become the first tennis player to compete in five Olympic Games and, at 36, will be the oldest player to compete in the women's singles since tennis returned to the Olympics in 1988.
The American sisters are top seeds in the doubles, having won together in London, and will face Czech duo Lucie Safarova and Barbora Strycova in the first round.
Several top names, including 17-time Grand Slam champion Roger Federer and Wimbledon runner-up Milos Raonic, are missing from the men's draw. The 2008 Olympic champion Rafael Nadal of Spain is in Rio despite not playing since pulling out of the French Open with a wrist injury.
Third seed Nadal, a potential semifinal opponent for Djokovic, faces Argentine Federico Delbonis in round one.
Murray, who will play with brother Jamie in the men's doubles, is line for a semifinal against Japan's fourth seed Kei Nishikori who plays Spain's Albert Ramos-Vinolas in round one of the hardcourt tournament that begins on Saturday.
Women's second seed Angelique Kerber of Germany begins her medal quest against Colombian Mariana Duque-Marino.
French Open champion Garbine Muguruza will play former world No. 1 Jelena Jankovic while another standout clash pits American Sloane Stephens against Canada's Eugenie Bouchard.
The Olympic events also include mixed doubles.
Opelka surprises Anderson
In Atlanta, Reilly Opelka saved two match points en route to upsetting third seed Kevin Anderson 6-7 (5-7), 6-3, 7-5 and advancing to the quarterfinals of the ATP Tour's Atlanta Open.
The 2.11 meter tall (6-foot-11) Opelka, who is ranked 556th in the world, registered his first win over a top 30 ATP opponent.
Opelka received a wild-card entry into the Atlanta tournament. The 2015 Wimbledon junior champion next faces seventh-seeded Donald Young, who rallied to beat Tim Smyczek 4-6, 7-6 (7-1), 6-3.
Young trailed 3-0 in the second set before seizing control. Top-seeded John Isner cruised into the quarterfinals with a 6-4, 6-0 rout of France's Adrian Mannarino.
