Djokovic-Nadal in potential semi clash

Defending champion Novak Djokovic and fellow two-time winner Rafael Nadal were drawn for a potential US Open semifinal clash on Friday. Djokovic, the top seed who has been nursing a wrist injury since a shock first round loss at the Olympics, begins his campaign against big-serving Jerzy Janowicz of Poland.

Janowicz, a Wimbledon semifinalist in 2013, has been plagued by knee trouble in recent months and has seen his ranking slump to 228 in the world. The fourth-seeded Nadal faces Denis Istomin of Uzbekistan in his first round. Second seed and Olympic champion Andy Murray, the 2012 winner, starts against Lukas Rosol of the Czech Republic.

The two clashed in an angry match in Munich last year where Murray described Rosol as one of the most hated players on the tour. With Roger Federer missing the tournament due to a knee injury which has shut down his season, fellow Swiss Stan Wawrinka takes the third seeding.

Wawrinka begins against Spain's Fernando Verdasco and could face fiery Australian Nick Kyrgios in the round of 16. In the women's draw, Serena Williams, bidding for a seventh US Open title and a modern era record 23rd Grand Slam, begins her campaign against the experienced Ekaterina Makarova of Russia.

Makarova beat Williams in the round of 16 at the Australian Open in 2012. Williams, 34, comes into the US Open after suffering a shoulder injury which forced her out of the Cincinnati event last week.

Second seed Angelique Kerber, the Australian Open champion, starts against Slovenia's Polona Hercog. Third seed Garbine Muguruza of Spain, the reigning French Open champion, and fourth-seeded Agnieszka Radwanska of Poland start against qualifiers.

Fifth seed Simona Halep of Romania meets Kirsten Flipkens of Belgium in the first round. Halep and Williams could meet in the quarterfinals. Earlier on Friday, America's world number 25 Sloane Stephens withdrew from the US Open with a right foot injury.