STANFORD, Calif. — Maria Sharapova took what she learned from a clumsy early win and turned it into a sharp, emphatic victory over fellow Russian Nadia Petrova in a second-round match Wednesday 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.

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.