New York - Three-time defending champion Serena Williams begins her quest to complete a calendar-year Grand Slam while past winners Novak Djokovic and Rafael Nadal launch their campaigns Monday at the US Open.
World number one Williams has already captured the Australian and French Open and Wimbledon crowns this season and could be the first person since Steffi Graf in 1988 to capture all four major women's singles tennis crowns in the same year by hoisting the trophy at the end of the Flushing Meadows fortnight.
That would give Williams 22 career Grand Slam singles titles, matching Graf's Open Era-mark and move her two shy of Australian Margaret Court's all-time record.
"I don't feel that pressure," Williams said of the intensity of making more history. "If I make it far, maybe I'll start to feel pressure. But as of now I really don't feel any."
Williams felt pressured at Wimbledon, where she won her fourth Slam crown in a row to complete the second "Serena Slam" of her career, giving her all four major trophies at the same time.
In all, Williams owns six Wimbledon, US Open and Australian Open singles titles plus three French Open crowns.
Williams will play the first night match at Arthur Ashe Stadium after opening ceremonies against Russia's Vitalia Diatchenko.
Following her onto the main stadium will be eighth seed Nadal opening against Croatian Borna Coric, who beat the Spaniard at Basel last year in their only prior meeting.
"He's a tough player. He's a young player with a lot of energy and he's a big competitor," Nadal said. "He's one of the players who is the future of our sport, so it's a tough one. But I'm playing well. I feel like I'm ready."
Nadal is on a quarter-final collision course with world number one Djokovic, who has the first feature men's match in Arthur Ashe Stadium when he faces Brazil's Joao Souza in an afternoon affair.
Djokovic seeks his third Grand Slam title of the year. He would be joining Williams in going for the season Slam had he beaten Swiss Stan Wawrinka in the French Open final.
"I feel like I'm well prepared," Djokovic said. "I've had a lot of matches so that competitive mode is going to help me ease my way into the tournament."
Last year's US Open men's finalists are both in action as well, with fourth seed Kei Nishikori of Japan meeting France's Benoit Paire and defending champion Marin Cilic, the ninth seed from Croatia, facing Argentine qualifier Guido Pella.
Nishikori beat Cilic on his way to the Washington title in their first rematch since last year's final. They could meet again in this year's quarter-finals.
On the women's side, the withdrawal Sunday of Russian third seed Maria Sharapova has left Serbian seventh seed Ana Ivanovic as the top-rated rival in Williams' half of the draw. They could meet in a semi-final.
Williams' older sister Venus, a seven-time Slam singles champion, and Swiss teen Belinda Bencic, who beat Serena in a Toronto semi-final two weeks ago, could be quarter-final hurdles to Serena's Slam bid.
Ivanovic opens against Slovakia's Dominika Cibulkova while Venus Williams opens against Puerto Rico's Monica Puig and Bencic opens against Bulgarian Sesil Karatantcheva.