Sharapova sees off battling Zheng at French Open

The second seeded Russian will take on America's Sloane Stephens, who she beat comfortably on clay in Rome two weeks ago, for a place in the quarter-finals.

But the 26-year-old Russian has work to do ahead of that encounter after dropping serve four times against Zheng and serving up eight double faults.

The pain of her 34 unforced errors was at least partially soothed by her 25 winners.

"I was lucky to get through that second set. I was a break down so I am happy to pull it through in straight sets," she said.

"It's not over until the last point is played and I felt like I was playing with a lot of energy out there."

Sharapova, playing in her 11th French Open, had reached the third round for the loss of just nine games and seemed on course for another routine win on Saturday.

Four breaks of serve helped her to the first set as her 43rd-ranked opponent failed to hold serve once while winning only nine points off the Russian's serve.

However, two breaks took the 29-year-old from Chengdu out to a 4-1 lead in the second before Sharapova turned up the heat again.

The champion pulled level at 4-4, pumping up the volume levels at the same time, only to hand Zheng the initiative again as the Chinese player broke for 5-4.

Zheng, who became the first Chinese woman to make the last 16 of a major when she played in the fourth round in Paris in 2004, was unable to serve out the set as Sharapova broke for 5-5.