Published: Aug 14, 2012 12:54 AM EDT
Updated: Aug 14, 2012 6:32 AM EDT

CINCINNATI (AP) - Serena Williams arrived at the Western & Southern Open with an Olympic gold medal and a chance to win another tournament she had never won before.

Really, Serena, you haven't won here before.

During a pre-tournament news conference Monday, Williams was confused about whether she had taken a title in Cincinnati.

"I did win this tournament, didn't I?" she said. "Maybe I didn't. I can't keep up. I don't think I did. OK. Whoops."

She has played the Cincinnati tournament three times, her best showing a semifinal loss in 2006.

Williams is scheduled to open play Tuesday night. The women's tournament began Monday and was capped later in the night by Shuai Peng's 5-7, 7-5, 7-6 (8) upset of 13th-seeded Jelena Jankovic of Serbia in a match delayed 40 minutes by rain.

Jankovic, last year's runner-up and the 2009 champion, lost at love while serving for the match in the second set, including a double-fault at love-40, and blew a total of five match points against her Chinese opponent.

Williams followed-up her Wimbledon championship in July by overwhelming Maria Sharapova 6-0, 6-1 to win the Olympics singles title.

The 31-year-old, ranked No. 4 in the world and seeded second at the $5.7 million event, spent a week training in Paris before arriving in Cincinnati. She still was basking in the glow of winning both the singles and, with older sister Venus, the Olympic doubles championship.

"It was really awesome to win both medals at the Olympics," she said.

And those gold medals are safely tucked away.

"My gold medals are in a location I probably shouldn't say, in case someone wants to go and take them," she said. "They're not with me."

Williams now can turn her attention to closing out her hard court season, which ends with the U.S. Open starting Aug. 27 in New York. She said he recent success on grass does not have her wishing to play on it more.

"I actually never really liked grass. It's never been my favorite surface. Now, I like it, but I love hardcourts," she said.

Thirteenth-seeded Alexandr Dolgopolov became the first player upset at Cincinnati, falling to 50th-ranked Nikolay Davydenko 6-1, 6-1 in the first round Monday.

Davydenko, ranked as high as No. 3 on the tour in 2006 and 2007, needed just 52 minutes to oust Dolgopolov, who was coming off winning the Citi Open in Washington on Aug. 5.

Dolgopolov, a Ukrainian ranked 16th in the world, committed 26 unforced errors to just three by his Russian opponent.

Twelfth-seeded Marin Cilic of Croatia survived a challenge from qualifier Sergiy Stakhovsky before advancing with a 6-3, 4-6, 6-4 win.

In other men's action on the tournament's first full day, Andreas Seppi of Italy beat the Netherlands' Robin Hasse 6-4, 6-4; qualifier Jesse Levine beat Donald Young 6-4, 7-6 (2) in a matchup of Americans; Taiwan's Yen-Hsun Lu eliminated Poland's Lukasz Kubot 6-3, 6-0; and American wild-card Brian Baker outlasted Philipp Kohlschreiber of Germany 7-6 (7), 7-6 (4).

Also, Serbian Victor Troicki beat Croatian qualifier Ivan Dodig 6-4, 7-5, Spain's Pablo Andujar cruised past Australian qualifier Marinko Matosevic 6-4, 6-3, German Florian Mayer defeated qualifier Fabio Fognini of Italy 7-5, 6-2, and Uzbekistan's Denis Istomin eliminated France's Julien Benneteau 6-3, 6-1.

Stanislas Wawrinka of Switzerland needed three sets to get by French qualifier Paul-Henri Mathieu 6-2, 3-6, 6-1. And Lleyton Hewitt advanced with a 6-4, 6-4 win over Russian Mikhail Youzhny.

The women's tournament got under way with a mild upset as 66th-ranked Timea Babos, a 19-year-old Hungarian, knocked out 39th-ranked Varvara Lepchenko of the United States 7-6 (4), 6-4. Babos lost in the final round of qualifying on Sunday but reached the main draw when Ana Ivanovic withdrew because of a toe injury.

Eleventh-seeded Dominika Cibulkova of Slovakia earned a routine 6-3, 6-4 win over qualifier Akgul Amanmuradova of Uzbekistan.

In other women's action, No. 11 seed Dominika Cibulkova of Slovakia earned a 6-3, 6-4 win over qualifier Akgul Amanmuradova of Uzbekistan; Italy's Mona Barthel beat Spain's Maria Jose Martinez Sanchez 6-0, 6-4; Anabel Medina Garrigues of Spain defeated Romanian Simona Halep 6-3, 6-0; Germany's Julia Goerges won in straight sets over Israel's Shahar Peer 6-3, 6-3; and Sweden's Johanna Larsson beat Australia's Casey Dellacqua 6-1, 6-3.

Also, wild card Camila Giorgi eased past fellow Italian Francesca Schiavone 6-1, 6-3; and Eleni Daniilidou of Greece outlasted Vania King of the United States 6-3, 2-6, 7-6 (6) in a matchup of qualifiers.

In the women's first completed night match, qualifier Urszula Radwanska of Poland advanced with a 6-2, 6-4 win over Ksenia Pervak of Kazakhstan.