Stosur cruises, Tomic tanks

Top seed Samantha Stosur powered her way into the Japan Open quarter-finals with a straight-sets win over local hope Misaki Doi on Thursday.

After suffering a massive scare in her opening-round win over Thai Noppawan Lertcheewakarn, the US Open champion had a much easier time of it against Doi, hitting five aces in her 6-2 6-4 victory in one hour and 22 minutes.

Next up for the world No.6 will be South Africa's Chanelle Scheepers, after the seventh seed edged past Kazakhstan qualifier Yaroslava Shvedova 4-6 6-3 7-6 (7-5) in two hours and 19 minutes.

Scheepers leads the head-to-head battle 2-1 over Stosur, although the pair have not clashed since 2003.

Sixth seed Ayumi Morita is also through after she accounted for Greek Eleni Daniilidou 6-2 6-3 in just under two hours.

Morita will face 2006 Japan Open winner Marion Bartoli in the quarter-finals, the Frenchwoman overpowering American Vania King 6-1 6-2 in one hour and 12 minutes.

The second-seeded Bartoli has won all six of her encounters with Morita - and it will be their fourth meeting in 2011 alone.

Meanwhile, the news wasn't as good for Stosur's compatriot Bernard Tomic who exited the Shanghai Masters after losing to Ukrainian Alexandr Dolgopolov 5-7 6-1 6-0.

The Aussie teenager started brightly taking out the first set but crashed in a heap to only win one game in the last two sets and managed just eight points in the third set.