Images: Venus withdrawal eclipses U.S. Open action

The U.S. Open witnessed a major shock without a ball being struck in anger on Wednesday when Venus Williams quit the tournament after revealing she was suffering from an illness that could threaten her tennis future.

After a buildup to the last Grand Slam of the year in which the event was threatened by an earthquake then a hurricane, the American's revelation was perhaps the most earth-shattering news of the week.

The two-time champion told officials of her withdrawal from the tournament less than an hour before she was due to face Germany's Sabine Lisicki in the second round.

Then she dropped the bombshell, revealing for the first time exactly what had kept her recent playing time down to a bare minimum.

"I have recently been diagnosed with Sjogren's Syndrome," she said in a statement. "(I) wish I could continue but right now I am unable to."

The disease drains victims of their energy and causes joint pain. For a professional tennis player, that spells trouble but Williams said she had no thoughts of retiring.

"I am thankful I finally have a diagnosis and am now focussed on getting better and returning to the court soon," she said.

At 31, speculation about her future in the sport is sure to intensify but fellow American Andy Roddick, who has been friends with the Williams sisters since they were children, said her health was the most important issue.

"I do know one thing. I'm very concerned, because if Venus isn't playing at the U.S. Open, it's got to be something," he said.

"She didn't withdraw because she's sneezing too much."

Williams was not the only high-profile casualty at Flushing Meadows on Wednesday but her illness did overshadow most of the on-court action.

Andy Murray, Britain's perennial major hope, made a bright start to his campaign while Argentina's Juan Martin Del Potro enjoyed a successful return to Flushing Meadows two years after his stunning title success.

However, three seeded women made early exits at the hands of lower-ranked players.

Marion Bartoli, Dominika Cibulkova and Yanina Wickmayer all departed while the only male seed to lose was Nicolas Almagro of Spain, although sixth seed Robin Soderling pulled out because of injury.

The Swede had been regarded as one of the few players able to challenge the big four of Roger Federer, Rafa Nadal, Novak Djokovic and Murray, but threw in the towel before his first round match.

Del Potro upset Federer to win the men's title two years ago but was unable to defend it because of a wrist injury that sidelined him for nearly nine months.

He finally returned to the scene of his greatest triumph and the towering Argentine was in a hurry to make up for lost time, crushing Italy's Filippo Volandri 6-3, 6-1, 6-1.

"It's my favourite tournament," Del Potro said. "I'm really happy to get the opportunity to play here again."

Somdev Devvarman let it slip after good start to go down in straight sets against fourth seed Andy Murray in the men's singles opening round but India rounded off a second successive all-win day in the doubles competitions of the U.S. Open here.

Somdev, India's lone men's singles competitor, lost 6-7, (5) 2-6, 3-6 against the British number one in a match lasting two hours and 27 minutes at the Arthur Ashe Stadium.

However, Sania Mirza, ousted from the singles event, and Leander Paes moved into the second round of the women's doubles and mixed doubles' competitions respectively after winning their opening matches.

The 26-year-old Somdev took advantage of the rusty start by Murray, who dropped an early break and struggled to keep the ball inside the lines.

Somdev controlled the tempo initially with some nifty net play, challenging Murray with drop shots and making his fancied opponent run around.

Elsewhere, India had a good day in the doubles arena. In women's doubles, sixth seeds Sania and her Russian partner Elena Vesnina eased past Americans Samantha Crawford and Madison Keys 6-2, 6-0.

In mixed doubles, Vesnia teamed up with Leander Paes to beat the Russian-British combine of Nadia Petrova and Jamie Murray.

The seventh-seeded Indo-Russian team won 6-2, 6-7, (7) 1-0 (6).

The women's draw, already depleted by the absence of Kim Clijsters and the early defeats of Petra Kvitova and Li Na, lost Bartoli to American Christina McHale and Cilbulkova to Irina Falconi, another American, giving rise to hope that the U.S. may eventually find a successor to the Williams sisters.

Russia's Vera Zvonareva, last year's runner-up, was never in any real danger of joining the casualty list even though the second seed had a tough workout against Ukraine's Kateryna Bondarenko before triumphing 7-5, 3-6, 6-3.

Third seed Maria Sharapova concluded the day with a late night 6-1, 6-1 romp past Anastasiya Yakimova of Belarus in a match that started in August and finished in September because it trickled past midnight.

"A big part of our sport is adjusting to whatever comes our way, whether it's the time of a match or opponents or conditions on the court," Sharapova said.

"It's one of the toughest things in our sport: sometimes you never know exactly what you're going to get," she added.