Novak Djokovic

Age: 26

Birthplace: Belgrade, Serbia

World ranking: 1

Grand Slam titles/U.S. Open titles: 6/1

Best shot: The Serb played brilliantly in the Wimbledon final, but fell to Andy Murray in straight sets. The loss seems to have left a mark. He faces a tough draw, needing to beat Andy Murray in the semis, in all likelihood, just to reach the final.

Rafael Nadal

Age: 27

Birthplace: Manacor, Spain

World ranking: 2

Grand Slam titles/U.S. Open titles: 12/1

Best shot: After a shocking first-round ouster at Wimbledon, the Spaniard has compiled the most dominant hard-court season, winning back-to-back Masters as a tuneup. But tendinitis in his knees is a chronic worry.

Andy Murray

Age: 26

Birthplace: Dunblane, Scotland

World ranking: 3

Grand Slam titles/U.S. Open titles: 2/1

Best shot: The Scot unloaded an epic burden in July, becoming the first British man to win Wimbledon in 77 years. He hasn’t played much nor looked too sharp since. He’ll need a quick turnaround to defend his 2012 U.S Open title.

Juan Martin del Potro

Age: 24

Birthplace: Tandil, Argentina

World ranking: 6

Grand Slam titles/U.S. Open titles: 1/1

Best shot: The 6-foot-6 Argentine hasn’t advanced beyond the quarterfinals of a major since winning the 2009 U.S. Open. But when his big serve and forehand are clicking, as they have of late, he’s capable of toppling the world’s best.

Serena Williams

Age: 31

Birthplace: Saginaw, Mich.

World ranking: 1

Grand Slam titles/U.S. Open titles: 16/4

Best shot: The most dominant player in women’s tennis showed rare vulnerability in losing a three-set final to Victoria Azarenka earlier this month. That defeat may prove her biggest incentive en route to a fifth U.S. Open title.

Victoria Azarenka

Age: 24

Birthplace: Minsk, Belarus

World ranking: 2

Grand Slam titles/U.S. Open titles: 2/0

Best shot: The hard-hitting, high-pitched shrieker from Belarus is among the few on tour who don’t fear Williams. She lacked the mental toughness to protect her lead in last year’s U.S. Open final but should get another chance this year.

Li Na

Age: 31

Birthplace: Wuhan, China

World ranking: 6

Grand Slam titles/U.S. Open titles: 1/0

Best shot: Maria Sharapova’s withdrawal left only a handful of contenders who have won majors, apart from Williams and Azarenka. Li, the 2011 French Open victor, is one. But she has yet to get past the U.S. Open’s quarters.

Sloane Stephens

Age: 20

Birthplace: Plantation, Fla.

World ranking: 17

Grand Slam titles/U.S. Open titles: 0/0

Best shot: The rising American is loaded with talent and excels on big stages, reaching the round of 16 or better in all three majors this year. She has beaten the top-ranked Williams and No. 3 Sharapova but struggles with consistency.