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Wozniacki, seeded nine this year and a quarter-finalist in 2010, breezed past Jarmila Gajdosova 6-1, 6-4 for a sixth win in six meetings against the Australian.
Gajdosova, now at 72 in the world after playing as a seed in Paris 12 months ago, paid a heavy price for her 40 unforced errors on a chilly Philippe Chatrier court.
Denmark's Wozniacki will face either Kaia Kanepi of Estonia or Romania's Irina-Camelia Begu for a place in the last 16 where she had originally been scheduled to meet Serena Williams.
But the great American's stunning loss to France's Virginie Razzano on Tuesday has removed the most formidable obstacle preventing a quarter-final between Wozniacki and Sharapova.
Fourth seeded Czech Petra Kvitova coasted into the third round with a 6-1, 6-3 win over Poland's Urszula Radwanska.
Wimbledon champion Kvitova, who only dropped three games in her opening win over Australian teenager Ashleigh Barty, needed 70 minutes to set up a clash with Russia's Nina Bratchikova.
The 22-year-old has twice reached the fourth round in Paris, including last year when she was defeated by China's Li Na and she never looked in trouble on Thursday.
She fired 30 winners past the 21-year-old Pole, the younger sister of third seeded Agnieszka Radwanska who had put out Venus Williams on Wednesday.
"She played well, she has good hands and a good touch," said 22-year-old Kvitova of her 79th-ranked opponent.
"But she wasn't very aggressive so I was able to play my game."
The first seed to lose on Thursday was Russian 16th seed Maria Kirilenko who, under the concerned gaze of ice hockey superstar boyfriend Alex Ovechkin, slumped to a 6-4, 3-6, 6-3 loss to the Czech Republic's Klara Zakopalova.
Zakopalova has made the third round for the first time in nine attempts and will face Russian 22nd seed Anastasia Pavlyuchenkova, who put out Melinda Czink of Hungary 4-6, 6-3, 6-3, for a place in the last 16.
Later Thursday, second seed Sharapova, who didn't drop a game in her opening win over Romania's Alexandra Cadantu, takes on Japan's world number 84 Ayumi Morita.
Defending champion Li Na, the seventh seed, faces France's Stephanie Foretz Gacon while Razzano goes up against Dutchwoman Aranxta Rus who knocked out Kim Clijsters in the second round in 2011.
Latest results from the fifth day of the 2012 French Open at Roland Garros on Thursday (x denotes seeded player):
Men
Second round
Andy Murray (GBR x4) bt Jarkko Nieminen (FIN) 1-6, 6-4, 6-1, 6-2
Jo-Wilfried Tsonga (FRA x5) bt Cedrik-Marcel Stebe (GER) 6-2, 4-6, 6-2, 6-1
David Goffin (BEL) bt Arnaud Clement (FRA) 3-6, 7-6 (7/2), 0-6, 6-1, 6-1
David Ferrer (ESP x6) bt Benoit Paire (FRA) 6-3, 6-3, 6-2
Milos Raonic (CAN x19) bt Jesse Levine (USA) 6-4, 7-5, 6-2
Juan Monaco (ARG x13) bt Lukas Rosol (CZE) 7-6 (7/4), 6-0, 7-6 (7/5)
Santiago Giraldo (COL) bt Bernard Tomic (AUS x25) 6-4, 6-1, 6-3
Mikhail Youzhny (RUS x27) bt Robin Haase (NED) 6-3, 7-6 (7/5), 6-4
Women
Second round
Petra Kvitova (CZE x4) bt Urszula Radwanska (POL) 6-1, 6-3
Klara Zakopalova (CZE) bt Maria Kirilenko (RUS x16) 6-4, 3-6, 6-3
Anastasia Pavlyuchenkova (RUS x22) bt Melinda Czink (HUN) 4-6, 6-3, 6-3
Caroline Wozniacki (DEN x9) bt Jarmila Gajdosova (AUS) 6-1, 6-4
Angelique Kerber (GER x10) bt Olga Govortsova (BLR) 6-3, 6-2
Nina Bratchikova (RUS) bt Claire Feuerstein (FRA) 3-6, 6-3, 7-5
