Sharapova had four breaks -- three in the second set -- in a 6-4, 6-3 win over 17th-seeded Sloane Stephens. Sharapova, who has yet to lose a set in the tournament, dropped serve just once and won about three-quarters of the points on serve.
She had a seventh-game break in the first set for a lead that she consolidated with two love games serving. After trading breaks to open the second set, Sharapova gained a 3-2 advantage with a break to end a 12-point game and later put the match away with a quick break.
She goes into the quarterfinals against 18th-seeded Jelena Jankovic, who breezed through a 6-0, 6-2 win over Jamie Hampton. After the first-set shutout, Hampton managed a break but Jankovic won the next four games for control of the match.
Third-seeded Victoria Azarenka, who has lost just one set in the French Open, opened the day's schedule with a brisk 6-3, 6-0 romp past Francesca Schiavone. Azarenka had seven breaks but she needed four in the first set as she only held serve twice in four games.
In the second set, however, Azarenka lost only nine points total, including four when Schiavone served.
No. 12-seeded Maria Kirilenko earned the quarterfinal spot opposite Azarenka with a 7-5, 6-4 win over Bethanie Mattek-Sands. Kirilenko won only five more (80-75) points than Mattek-Sands but had two breaks in each set.