Sharapova, the No. 2 seed who needs a French Open title for the career Grand Slam, got past Klara Zakopalova 6-4, 6-7 (5-7), 6-2. The match featured 21 breaks in 30 games and fittingly ended with Sharapova's 12th break of the day.
Sharapova dropped her serve just once and lost a total of five games in sweeping through the first three rounds but Zakopalova proved stubborn throughout the match. Zakopalova finished off nine of her 17 break chances and had 44 winners.
Sharapova overcame 53 unforced errors and 12 double faults in advancing to the quarterfinals. She has twice been a semifinalist in Paris, including last year when she lost to Li.
Li, the No. 7 seed, fell to qualifier Yaroslava Shvedova 3-6, 6-2, 6-0. Shvedova, who has lost just one set in the main draw, took 58 percent of the points in the final two sets. She didn't manage a break point in the first set but converted seven of 19 the rest of the way.
Li had 41 unforced errors, nearly twice as many as Shvedova's 21.
Sharapova draws 23rd-seeded Kaia Kanepi in the quarterfinals after Kanepi beat Arantxa Rus 6-1, 4-6, 6-0. Kanepi had eight breaks, including her first two in the third set at love.
Shvedova, who hadn't advanced out of the third round of a Grand Slam event before this tournament, will next play No. 4-seeded Petra Kvitova, who was a 6-2, 6-1 winner Monday over Varvara Lepchenko in just 60 minutes.