Russian big-hitter Maria Sharapova on Tuesday overwhelmed Samantha Stosur of Australia in a swift 6-0, 6-1 victory as other top players suffered early exits at the Pan Pacific Open.

The former world number one fired seven aces and hit a first-serve percentage of 71, in addition to a barrage of sizzling shots that ended the match in 57 minutes at the Ariake Colosseum.

"So far, I feel like I have been serving really, really well," Sharapova said.

Winner in 2005, she said she has focused on serving as ne of her practice priorities since a disappointing showing at the US Open earlier this month.

The 22-year-old is one of a few top-class players remaining in this $2-million event after a series of second-round upsets ousted top-ranking players.

The world number one Dinara Safina of Russia, number three Venus Williams of the United States and number four Elena Dementieva, also of Russia, were all ousted in the first two days.

French Open champion Svetlana Kuznetsova has also been eliminated.

"I think it just shows the competitiveness of women's tennis today, and how much everyone is improving," Sharapova said.

"You are seeing many three-setters. That's a real indication of the strength and depth of the game right now," she said.

Asked whether she felt pressure to take the tournament, Sharapova said her focus was just on her next match.

"I think it is just a matter of taking one match at a time, and really focusing on the task that's ahead, instead of thinking of too far ahead in the tournament," she said.

Sharapova returned to the top professional circuit in May after a nine-month injury layoff during which she underwent surgery on her right shoulder.

She said she hoped to end the season "on a good note and have a good off-season".