Nadia Petrova of Russia returns the ball in her suprise win over Ivanovic [AFP]

Top seed Jelena Jankovic blazed into the quarter-finals of the Pan Pacific Open with a crushing 6-2 6-1 victory over Italian Flavia Pennetta.

But fellow Serb Ana Ivanovic suffered a shock exit when the French Open champion was upset 6-1 1-6 6-2 by Russian Nadia Petrova in her opening match on the shore of Tokyo Bay.

Jankovic, beaten by Serena Williams in the US Open final earlier this month, will recapture the world number one ranking from the American if she wins in Japan.

Jankovic dominant

The Serbian overpowered Pennetta in a match played under a closed roof because of an approaching typhoon, wrapping up an easy win with an ace after just 61 minutes.

"I would like to be number one again," Jankovic said.

"But the most important thing is to finish the year as the number one player."

Jankovic faces Russian Svetlana Kuznetsova next after the fifth seed crushed Japan's Ayumi Morita 6-1 6-1.

Second seed Ivanovic, who had declared herself fully fit after withdrawing from last month's Beijing Olympics with a thumb injury, lost after an error-strewn performance.

Olympic champion Dementieva skips into the quarter-finals [AFP]

Fast surface

"I haven't played many matches so I'm happy to get back playing again," she said.

"It was obviously frustrating but the surface was very fast and she was going for her shots."

Earlier, Olympic champion Elena Dementieva booked her place in the season-ending WTA Championships by crushing France's Alize Cornet 6-0 6-3 in her opening match.

The world number four, who won gold in Beijing last month, took just 69 minutes to reach the last eight of the $1.34 million Pan Pacific tournament.

Dementieva on form

Dementieva, the Pan Pacific Open's third seed, became the fifth player to qualify for November's showcase event in Doha, exclusive to the world's top eight.

"It's great to be there months before," said the Russian, winner in Tokyo two years ago.

 "I remember years before fighting right up to the end to get into the tournament."

Williams, Jankovic, Ivanovic and Russian Dinara Safina have already secured their spots in the $4.45 million end-of-season shootout.

Recommend this article...

Did you enjoy this article? Please bookmark it onto: