CINCINNATI — 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.