{blackbabes} Williams reaches semifinals at Stanford

STANFORD, Calif. (AP)—Serena Williams stumbled once, unable to plant her right foot. It was one of the few times she looked vulnerable Friday night.

The unseeded Williams put on a clinic with precision serving and a sharp ground game to get the better of second-seeded Maria Sharapova, 6-1, 6-3, in the quarterfinals of the Bank of the West Classic.

Playing in just her third tournament since winning Wimbledon last year, and her first on American soil since the 2009 U.S. Open, Williams looked as good as she did when she topped the rankings.

The fifth-ranked Sharapova had eight unforced errors before she hit her first winner and the slow start cost her in the battle of former No. 1s.

Williams, currently ranked No. 169, beat Sharapova for the sixth straight time and improved to 7-2 overall against her.

Sharapova last beat Williams at the 2004 WTA championships.

Germany's Sabine Lisicki knocked off her second straight seeded opponent, beating fifth-seeded Agnieszka Radwanska of Poland 7-6(4), 2-6, 6-2. She will meet Williams in the semifinals.

Lisicki was a semifinalist at Wimbledon and has improved her ranking to 26th after being No. 218 in March.

"I'm looking forward to the match," Lisicki said. "I love competing in the big matches. I have nothing to lose."

Sharapova beat Lisicki in the semis at Wimbledon.

"Coming from grass to hardcourt is always a challenge," Lisicki said. "It comes down to who plays the best that given day."

Last year, Lisicki missed five months with a left ankle injury. She says she has more endurance now than before her injury.

"I'm much better than I was before the injury," she said. "I've had to focus on so many aspects of my game. Last year I couldn't even walk. Now I feel I can rely on my serve when I need it at crucial moments."

Lisicki recorded 14 aces to Radwanska's seven.

The 14th-ranked Radwanska was a semifinalist at Stanford last year. She's still looking for her first tour title since 2008.

Third-seeded Marion Bartoli of France advanced when Japan's Ayumi Morita retired after dropping the first set 6-1. Bartoli will meet eighth-seeded Dominika Cibulkova of Slovakia, who beat qualifier Marina Erakovic 6-1, 6-1.

The 20th-ranked Cibulkova, looking for her first tour title, reached her second semifinal of the year.

"I was pretty solid the whole match," Cibulkova said. "I hope to keep playing at this level."