US Open 2015

Venue: Flushing Meadows, New York Dates: 31 August-13 September

Coverage: Online radio commentary of Heather Watson, plus live radio and text commentary on every Andy Murray match and selected others.

Kei Nishikori and Ana Ivanovic both made early exits on the opening day of the US Open in New York.

Japan's Nishikori, last year's runner-up and the fourth seed, lost 6-4 3-6 4-6 7-6 (8-6) 6-4 to Frenchman Benoit Paire.

Serbia's Ivanovic, the seventh seed, was beaten 6-3 3-6 6-3 by Dominika Ciblukova of Slovakia.

But men's top seed Novak Djokovic made easy progress, defeating Brazil's Joao Souza 6-1 6-1 6-1 to reach round two.

"I'm just hoping I can continue playing this way and if I do so I think I have a very good chance against anybody," said the Serb, who needed just 71 minutes to beat the world number 89.

On an opening day where a number of seeds were beaten, Nishikori said he hoped to "come back strong" next year.

"It's always very sad to lose in the first round, but I think he was playing good tennis so I don't think I played bad," said Nishikori, who beat world number one Djokovic at Flushing Meadows in 2014.

Defending champion Marin Cilic, who overpowered Nishikori in straight sets in last year's final, beat Argentine Guido Pella 6-3 7-6 (7-3) 7-6 (7-3).

Serena seeks the spotlight

Serena Williams

Serena Williams is aiming to create history in New York

The fact that the women's final has reportedly sold out before the men's for the first time this century highlights the interest surrounding world number one Williams in New York.

She won her fourth straight major title, dubbed a 'Serena Slam', at Wimbledon. Now she has the chance for her first calendar Grand Slam of all four majors in a year.

Her opening match against Russia's world number 86 Vitalia Diatchenko has been given prime-time billing as it opens the first night session at 00:00 BST.

The 33-year-old six-time champion will be calling on the Arthur Ashe Stadium crowd to help pull her through the next seven matches.

"It's the biggest stadium for tennis players in the world, it's the biggest stage in the world - New York," she said. "It doesn't get any bigger or better than this."

Draw opens up for Serena

Williams' chances of reaching the final were boosted even before she began her title defence as seeds tumbled to leave the American with no other top-10 player in her half of the draw.

As well as Ivanovic, eighth seed Karolina Pliskova - who lost 6-2 6-1 to Anna Tatishvili - and 10th seed Carla Suarez Navarro failed to progress, while Maria Sharapova withdrew on the eve of the tournament because of injury.

Williams' sister Venus, the two-time champion, did advance to the second round, beating Monica Puig - only her second victory since losing in the last 16 at Wimbledon.

Nadal faces early test

Rafael Nadal

Rafael Nadal was US Open champion in 2010 and 2013

Williams is expected to face little trouble in her opening match, and men's top seed Djokovic should see off Brazil's Joao Souza in the day's third match on Ashe, but there is danger lurking for two-time champion Rafael Nadal on day one.

The Spaniard has slipped to eighth in the seedings and faces 18-year-old Croat Borna Coric in the second night match at around 02:00 BST on Tuesday.

Nadal is struggling to recapture his best form, and lost his only previous meeting with Coric last year.