NEW YORK (AP) _ Olympic champions Rafael Nadal and Elena Dementieva showed their mettle at the U.S. Open, overcoming early challenges to win Monday 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.

No. 9 seed James Blake had to play past midnight to survive a five-set match against 19-year-old fellow American Donald Young. With the help of two key calls overturned on challenges in the last two games, Blake won 6-1, 3-6, 6-1, 4-6, 6-4.

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.

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.

In the night's last match, they got behind Young, the former No. 1 junior player in the world. Young came back from down a break to win the fourth set. Serving with the final set tied 4-4, he seemed to have the momentum.