Top seed Maria Sharapova [Images] demolished Sania Mirza [Images] 6-2, 6-1 to reach the semi-finals of the San Diego Classic on Friday.

Eleventh seeded Swiss Patty Schnyder was nearly as impressive as Sharapova, out-toughing number four Nadia Petrova of Russia [Images] 6-4, 6-4.

She will meet another Russian, ninth seed Elena Dementieva, who overcame compatriot Maria Kirilenko 6-2, 6-4.

India's Mirza came into the match loaded with confidence after reaching the final of the Stanford Classic last week and having beaten eighth seed Dinara Safina in the previous round in San Diego.

But she had trouble returning Sharapova's serves and watched the Russian tear apart her second serve.

Sharapova was in control for the entire match, with Mirza winning only 40 percent of her service points.

"I stepped inside the court and played my game," Sharapova told reporters.

"I wanted to make sure I stepped in and hit it. The two most important things were my serves and returns because she's pretty solid from the baseline." 

Playing in her first tournament since falling to Venus Williams in the fourth round of Wimbledon, defending champion Sharapova seems to have regained her stride and has lost only 10 games in her last three matches.

The former world number one has yet to win a title this year, but thinks her confidence may be returning.

"I'll take these matches rather than 7-6 in the third," Sharapova said.

"No matter how confident you are, you have to live in reality. I don't know where confidence comes from, but it's good to get these matches behind me and know I'm playing consistently and serving better."

Since returning to the tour after six weeks off due to three broken ribs in May, Dementieva has struggled to regain her once top five form.

But the former U.S. Open finalist said she feels at home on the hard court -- her favourite surface -- and ran Kirilenko ragged.

"It was difficult match," Dementieva said. "She plays very smart. I'm very happy to be back on the tour and playing well again."

Sharapova will meet third seed Anna Chakvetadze [Images], who handed Venus Williams her first San Diego Classic defeat since 1999.

Chakvetadze, the third seed who arrived here seeking her third title in as many weeks, defeated the Wimbledon champion 6-7 (5/7), 7-6 (7/3), 6-2.

 Chakvetadze struggled through a collapse in the first set, throwing away a 5-2 lead, missing on two set points and finally losing a tiebreaker.

But the 20-year-old hung tough, taking the second set in a decider as Williams stuffed an easy volley into the net after two hours on court.

The third set turned into a runaway for the Russian, who has now won a dozen straight matches. Williams was stunned after striking 79 unforced errors and missing on a match point.

"She saved her best for San Diego," Williams said. "I was not at my best level. I'm really tired and it showed. Lots of
things went wrong in my game tonight."

• Complete tennis coverage
• All you want to know about Sania Mirza