Hingis will face Maria Kirilenko in the last eight

The Swiss wild card, who has won the event four times, beat the French third seed 4-6 7-5 6-2 in Tokyo.

Hingis retired in 2002 due to injury but reached the last four in her comeback tournament before making the quarter-finals of the Australian Open.

Top seed Sharapova breezed past America's Lisa Raymond 6-4 6-4.

Dechy believes Hingis, 25, is returning to the form that brought her five Grand Slam titles between 1997 and 1999.

I survived a three-set match today, so I think the match fitness is quite there Martina Hingis

"Martina still takes the ball really early and still has unbelievably good hand-and-eye coordination," said Dechy.

"When she stopped playing before, she was good. And now, she has a lot of confidence from the Australian Open. Her steadiness and depth made it difficult for me during the whole match."

Hingis said: "In the last set and a half I started reading her returns and reacting better. Thank God I have still have those skills - that was a saviour."

"I survived a three-set match today, so I think the match fitness is quite there."

In the quarter-finals on Friday, Hingis will take on Maria Kirilenko of Russia, who beat eighth seed Ana Ivanovic of Serbia and Montenegro 6-4 6-4.

Sharapova will play Australia's Samantha Stosur, who beat sixth seed Daniela Hantuchova of Slovakia 7-6 6-2.

Russia's Elena Likhovtseva also booked her place in the last eight with a 6-2 7-5 win over Frenchwoman Marion Bartoli.

Likhovtseva now faces former French Open champion Anastasia Myskina, who became the fifth Russian to reach the quarter-finals with a 6-4 6-4 victory over Czech Klara Koukalova.