The fifth-seeded Williams, the only woman in the field who has won the clay-court major, had a 10-0 edge in aces.
“I guess I do have pressure,” Williams said, “but I don’t put pressure on myself.”
She ceded the first two games before winning 6-2, 6-1 in a drizzle against 61st-ranked Ashley Harkleroad, an American who’ll appear in the August issue of Playboy.
“I’m just surprised she beat me to it,” Williams said with a hearty laugh. “Darn.”
Two-time Grand Slam runner-up Ana Ivanovic struggled before beating Sofia Arvidsson 6-2, 7-5.
The first seeded player to lose was No. 15 Nicole Vaidisova. She reached the French Open semifinals in 2006 and the quarterfinals last year, but was upset by Iveta Benesova 7-6 (2), 6-1.
The second-ranked Ivanovic, who became the first player representing Serbia to play in a major final at last year’s French Open, had six double-faults on center court and was broken by her Swedish opponent when serving for the first set at 5-1.
“I let my intensity go down for a bit ... and she used it and she started playing much better,” Ivanovic said. “But towards the end I’m happy that I found back my game and managed to break her back, and win the second set.”
Ivanovic, who reached the final at this year’s Australian Open, was also broken in the third game of the second set. In her next service game, while trailing 3-1, Ivanovic saved three break points before holding. Then, after breaking Arvidsson to get to 3-3, the Serb saved two more break points.
In the final game, Ivanovic hit two forehands down the line to break Arvidsson and win the match.
“In the end it was close, but I didn’t win the important points,” Arvidsson said.
Ivanovic also beat Arvidsson in the first round at Roland Garros last year, winning 6-2, 6-0 on her way to the final, where she lost to Justine Henin. The Belgian is not defending her title, having announced her retirement this month.
“Last year I just broke into top 10, and I had much less pressure, honestly speaking,” Ivanovic said. “Now I’m No. 2, and obviously I have more expectations for myself. So that’s something I’m still learning how to deal with it.”
Ivanovic will face Lucie Safarova in the second round. The Czech player beat Sandra Kloesel of Germany 6-1, 6-1.
Vaidisova reached the fourth round at the Australian Open, but she has now lost six straight matches.
“It’s always hard to play your best friend,” the 19-year-old Vaidisova said.
Vaidisova double-faulted on match point to put the 70th-ranked Benesova into the second round at Roland Garros for the fourth time.
In the first set, Benesova jumped out to a 5-0 lead in the tiebreaker.
“The key point of the first set was the tiebreaker,” Benesova said. “I knew I had to come in and try to attack her and make her move. I was going for the big shots and it was working.”
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