NEW YORK — Olympic champions Rafael Nadal and Elena Dementieva showed their mettle at the U.S. Open, overcoming early challenges to win today in the start of what's expected to be a wide-open tournament.

Former champs Lindsay Davenport and Svetlana Kuznetsova also opened with straight-sets victories. Many of the stars like to hurry through the first round — it takes seven wins for the title, and any rest is welcome.

Playing for the first time as the world No. 1, Nadal swatted his very first shot wide against No. 136 Bjorn Phau. The Wimbledon and French Open champ was two points from dropping the first set when he surged and, despite needing to bandage a nasty blister, won 7-6 (4), 6-3, 7-6 (4).

"I didn't play with normal intensity," Nadal said. "Probably I'm a little bit tired."

Asked whether he was more worn down mentally, physically or emotionally from Beijing, he said: "I think it is a little bit of everything."

Nadal got a stiffer test from the German qualifier than many anticipated, and shook his head near the end of a match that lasted nearly 3 hours.

Dementieva looked like gold while taking the final four games to defeat Akgul Amanmuradova 6-4, 7-5. The fifth-seeded Russian was glad to win quickly and give her mind and body a break.

"It's very hard not to think about the Olympic Games," Dementieva said. "Very difficult to refocus. I mean, all my thinking is there in Beijing."

Tenth-seeded Anna Chakvetadze was the top player to lose, beaten by Ekateria Makarova 1-6, 6-2, 6-3 in a matchup of Russians.

James Blake and Jelena Jankovic led the lineup of Monday night matches.

Roger Federer, bidding for his fifth straight U.S. Open title, was scheduled to begin Tuesday, as were No. 1 Ana Ivanovic and the Williams sisters.

The final Grand Slam event of the season figured to be a scramble on both sides.

Nadal seems like the natural favorite, yet has never gone beyond the quarterfinals in five previous tries at Flushing Meadows. The 22-year-old Spanish dynamo took a while to find his rhythm against Phau, whose spirited play made him a crowd favorite.

Fans at Arthur Ashe Stadium, often quiet during early daytime sessions, cheered when Phau dived for a shot, rolled over on his back and chased a return.

The women's draw is even more tricky, now that 2007 champion Justine Henin has retired and Maria Sharapova is out with an injured shoulder.

Six different women have won the U.S. Open in the last seven years, and Dementieva is seeking her first major championship. To her, the Olympic singles title counts.

"The biggest goal for the year was Beijing," she said. "In Russia, if you stop anyone in the street and ask what is a Grand Slam, I don't think many people can tell you. But everyone knows the Olympic Games. There is nothing bigger."

During a quick stopover in Moscow to see her mom and drop off her gold medal, she found out how much the win meant.

"People just come to me and say, 'Oh, I'm happy for you. You're always losing in the final. It's so great that you finally win something big,"' she said.

Dementieva put together a workmanlike win over Amanmuradova. Her opponent from Uzbekistan served for the second set ahead 5-3, but Dementieva still had enough energy.

"I don't know what is best, to be a little bit tired but very comfortable and very positive, or to be fresh and not play in the Olympic Games," she said.

Li Na, who beat Venus Williams in Beijing, beat No. 24 Shahar Peer of Israel 2-6, 6-0, 6-1. The No. 23-seeded Davenport defeated Aleksandra Wozniak of Canada, 6-4, 6-2 and No. 3 Kuznetsova beat Zhang Shuai of China 6-4, 6-2.

No. 12 Marion Bartoli of France, No. 14 Victoria Azarenka of Belarus and No. 15 Patty Schnyer of Switzerland also won.

On the men's side, fourth-seeded David Ferrer of Spain beat Martin Vassallo Arguello of Argentina 7-6 (1), 6-2, 6-2 and No. 6 Andy Murray of Britain beat Sergio Roitman of Argentina, 6-3, 6-4, 6-0.

Also winning were No. 7 David Nalbandian of Argentina, No. 10 Stanislas Wawrinka and No. 16 Gilles Simon of France. The No. 29-seeded Juan Monaco of Argentina lost to Kei Nishikori of Japan 6-2, 6-2, 5-7, 6-2.