Maria Sharapova's rampage through the French Open lost a little steam Monday with a less-than-routine win over Klara Zakopalova of the Czech Republic.
The Russian world No. 2 had only dropped five games in her first three matches, but was made to work much harder against the world No. 50, prevailing 6-4, 6-7 (5), 6-2.
Sharapova sets up a quarterfinal against Kaia Kanepi of Estonia in her quest for the one missing Grand Slam in her collection. The two have never met.
Should she overcome the 23rd seed, Sharapova will not have to face defending champion Li Na in a rerun of last year's semifinal after the Chinese player was upset by Kazakhstan's Yaroslava Shvedova earlier Monday.
Li came back from a set down to beat Christina McHale of the U.S. in round three, but crumbled against Shvedova on Monday after taking the first set comfortably.
The final score was 3-6, 6-2, 6-0 in favor of the 24-year-old Moscow-born player, who switched allegiances from Russia in 2008.
Shvedova was as high as world No. 29 in 2010, when she also reached the Roland Garros quarterfinal, but a knee injury has since seen her slip down the rankings.
She faces either Varvara Lepchenko of the United States or fourth seed Petra Kvitova in the quarterfinals.
In the men's draw, local hero Jo-Wilfried Tsonga finished off Switzerland's Stanislas Wawrinka when play resumed after their marathon five-setter was interrupted by nightfall.
The fifth-seeded Frenchman had just managed to see off a fierce comeback from the 18th seed to go 4-2 up in the decider when bad light stopped play Sunday.
Tsonga rounded it off on Monday for a final scoreline of 6-4, 7-6 (6), 3-6, 3-6, 6-4 and a quarterfinal matchup with world No. 1 Novak Djokovic.
The 27-year-old has won only one round without dropping a set, against Italy's Fabio Fognini in round three.
Djokovic isn't at his freshest either after his own five-set slog against Andreas Seppi on Sunday.
Spain's Nicolas Almagro upset Djokovic's compatriot Janko Tipsarevic earlier to set up a quarterfinal with Argentina's Juan Monaco or second seed Rafael Nadal.
Almagro, the 12th seed, won in straight sets, 6-4, 6-4, 6-4.
Elsewhere, David Ferrer sauntered into the quarterfinals with a 6-3, 6-2, 6-0 win over Spanish compatriot countryman Marcel Granollers in less than two hours.
It was a second-straight thrashing doled out by the sixth-seeded Ferrer, who dismantled Mikhail Youzhny to such an extent that the Russian scrawled the word "sorri" into the clay to apologize to the crowd for his performance in the previous round.
Next up for Ferrer is British fourth seed Andy Murray or local favorite Richard Gasquet, the 17th seed.
