STANFORD, Calif. (AP) – Maria is back. Maria Sharapova took what she learned from a clumsy early win and turned it into a sharp, emphatic victory over fellow Russian Nadia Petrova on Wednesday in a second-round match at the $700 000 WTA Premier Bank of the West Classic. Sharapova needed just over an hour to beat 10th-ranked and fifth-seeded Petrova 6-1, 6-2 after a three-set win over Japan’s Ai Sugiyama on Monday.

“I knew what I had to improve upon,” Sharapova said. “I started that first match lousy. This time the goal was to get a better start.”

Sharapova, who played her 17th match since returning to the court from a nine-month layoff due to right shoulder surgery, also had a pretty finish.

“I was aggressive the whole way through,” she said. “I didn’t have many letdowns and even when I made unforced errors I stayed with it.”

The former world No.1 player improved to 13-4 on the season and beat Petrova for the seventh time in eight meetings.

Sharapova was pushed to three sets in their last match at the French Open.

“This is the easiest score line I’ve had against her,” Sharapova said. “Most of the time we go three sets. She’s explosive and always goes for her shot.”

In other second round matches, third-seeded and fourth-ranked Elna Dementieva beat Maria Kirilenko 6-1, 6-2; Samantha Stosur downed Monica Niculescu 6-1, 7-5; and Daniela Hantuchova upset seventh-seeded Agnieszka Radwanska 4-6, 7-6 (6), 6-1, in a match that lasted over two and a half hours.

Serena and Venus Williams warmed up for their second round singles matches with an efficient 6-1, 6-0 doubles victory over Liga Dekmeijere and Julie Ditty.

Britain’s Anne Keothavong, who left her doubles match after crashing into a fence Tuesday night, is out for the rest of the season. Tests on Wednesday morning revealed a severe left knee sprain.