Wimbledon champion Maria Sharapova had little difficulty in her first match at the $1.3 million Montreal Cup on Wednesday, downing Kristina Brandi of Puerto Rico 6-1, 6-4.

However, fourth-seeded Russian Elena Dementieva and eight-seeded compatriot Nadia Petrova were second-round upset victims on the third full day of competition at the event.

The 17-year-old Sharapova, the first Russian player to win Wimbledon, was challenged briefly in the second set but was able to quickly recover and put the match away with her dominating backhand and solid groundstrokes.

"She definitely picked up her game in the second set," the sixth-seeded Sharapova said.

"I never expect to play my best tennis in my first match, but I did everything I had to do to win."

Dementieva became the first major upset victim of the week, losing to Argentina's Gisela Dulko 6-1, 6-4.

Dulko, 19, is a WTA rookie who already has pulled off several upsets.

"I played well from the baseline and served pretty well," Dulko said.

"So that was the key to the match. She's the highest ranked player I've ever beat."

Petrova was also knocked out of the tournament, dropping a 6-4, 6-7, 7-5 decision to fellow Russian Elena Likhovtseva.

Third-seeded Anastasia Myskina, the French Open champion, moved on with an easy 6-0, 6-4 win over Arantxa Parra Santonja of Spain.

Other winners included ninth-seeded Paola Suarez of Argentina, number 10 seed Vera Zvonareva and Francesca Schiavone of Italy, the 11th-seed, who all recorded straight set victories.

In other matches involving seeded players, 13th-seeded Magdalena Maleeva of Bulgaria defeated Martina Sucha of Slovakia 6-3, 6-7, 6-4, 14th-seeded Elena Bovina of Russia stopped Lilia Osterloh 7-6, 6-4 and 15th-seed Chanda Rubin of the U.S. was a 6-4, 6-3 winner over compatriot Mashona Washington.