BEIJING — The biggest surprise on a dismal first day of Olympic tennis came from Ana Ivanovic, who didn't even play.

The top-seeded Ivanovic withdrew Sunday because of inflammation in her right thumb that has bothered her for several weeks. Her decision was announced after play was called for the day with only nine of 45 scheduled matches completed.

Ivanovic decided to pull out after trying to practice on the eve of her opening match.

"It was just too painful," the Serb said. "I haven't played at all the last 10 days. It's one of the hardest moments in my career. I'm very, very disappointed."

Among the few players to complete victories was James Blake, at No. 8 the top-seeded American in the men's draw.

Ten matches were suspended and 26 postponed. Serena Williams was interrupted with a one-set lead, and despite a long wait, Roger Federer never got on court.

No one was more frustrated than Ivanovic, nursing a swollen thumb joint at the top of her hand. She said the injury may take another two weeks to heal, which makes her questionable for the U.S. Open beginning Aug. 25.

"Hopefully it will be enough time," she said. "I went through so many treatments in the last five or 10 days, but with this injury it just takes time."

She was already assured of losing the top spot in the rankings Monday to No. 2 Jelena Jankovic. Ivanovic has led the rankings since June 9, the day after winning the French Open for her first Grand Slam title.

The medal chase began with Blake beating the rain and winning his Olympic debut. Playing the first center-court match, he erased a set point in the second set and defeated Chris Guccione of Australia 6-3, 7-6 (3).

Rain twice interrupted the second center-court match. After a 2½-hour delay accompanied by frequent thunder, play was suspended for the night with Williams leading Belarus' Olga Govortsova 6-3, 2-1.

Williams was making her Olympic singles debut. She won a gold medal in doubles in 2000 with her sister Venus.

The rain caused a heavy backlog for the tournament. Those reaching the medal rounds will have to play almost every day, because only seven days remain to complete six rounds. In addition, many players are entered in both singles and doubles, including the Williams sisters, Federer and Rafael Nadal.

Blake held every service game and earned the only break of the match for a 5-3 lead in the first set. He faced a set point at 5-6 in the second set but held, then hit five winners in the tiebreaker.

When Blake smacked an ace on match point, he threw a fist and shouted "Yeah!" as the stadium crowd of 4,000 applauded his first Olympic victory.

"Definitely more nerves than a normal match," Blake said. "I tend to not really get nervous when I'm out on a tennis court, but today was a little different."

Twice during the match, small clusters of fans chanted "U-S-A!" With Andy Roddick skipping the Olympics, Blake is the highest-seeded American man.

The start of the tournament was delayed 2½ hours because of rain, then began under thick smog. While Blake waited to play, he watched other events on TV, including Michael Phelps' record performance to win a gold medal in the 400-meter individual medley.

"Watching Michael Phelps set a world record, it was something that was special to me because it made me realize how many people are inspired by him, and that I'm now in the position to have that opportunity to go out there and get a medal for my country," Blake said. "Today was hopefully the first step toward that."

No. 4-seeded Nikolay Davydenko of Russia beat Latvia's Ernests Gulbis 6-4, 6-2. No. 12 Fernando Gonzalez, who carried the flag for Chile in the opening ceremonies, defeated Sun Peng of China 6-4, 6-4.

Ivanovic was replaced by Tzipora Obziler of Israel. Marin Cilic and Ivan Ljubicic of Croatia withdrew from men's doubles, and they were replaced by Dmitry Tursunov and Mikhail Youzhny of Russia.