Crowd-favourite Maria Sharapova stormed into the quarterfinals beating fellow Russian Alisa Kleybanova in the Pan Pacific Open on Wednesday.

The former world number one, the champion here in 2005, fired an array of lightning service return winners to come from behind to win 2-6, 6-2, 6-2 against her 29th-ranked compatriot.

Sharapova admitted that service return was the difference.

"I think on this quick surface, serve and return are pretty big keys to the game because the person can get an advantage on the point, a pretty good chance of finishing the point on a good note," she said.

"Especially like a player today whose strength is a big serve, you really want to take that away as much as you can and then you can take care of your own service game."

As for the first-set loss, Sharapova said: "She started off really good, she started off really strong. The rallies were long and she was just able to come up with a winner."

Sharapova, ranked 25th, double-faulted on a break point to lose the opening game and failed to recover the deficit as she hit a backhand shot into the net on Kleybanova's first set point.

But Sharapova was never really in danger after, finishing her fellow Russian off in just over two hours.

Another former world number one, Jelena Jankovic of Serbia, dominated Elena Vesnina before the Russian abandoned the match with a left thigh problem at 6-1, 3-0.

The seventh seed is the highest-ranked player left after some notable early casualties.

World number one and defending champion Dinara Safina, fellow Russians Svetlana Kuznetsova and Elena Dementieva, and American Venus Williams have all gone.

In the quarterfinals on Thursday, Jankovic will take on 14th seed Marion Bartoli of France, who outclassed Anastasia Pavlyuchenkova of Russia 4-6, 6-2, 7-5.

Sharapova will play Iveta Benesova of the Czech Republic, winner over qualifier Chang Kai-chen of Taiwan 7-5, 6-2. Chang shocked Safina in the second round on Monday.

In other third-round action, Asia's number one Li Na of China came from a set down and 4-5 to beat Kateryna Bondarenko of Ukraine 2-6, 7-5, 6-3.