Caroline Wozniacki looked short of her top-seed billing as she edged into the French Open third round with a 6-3 7-6 (8-6) win over Aleksandra Wozniak.
The 20-year-old Dane, still searching for her first Grand Slam title, had to save three set points to avoid Wozniack taking the contest to a decider.
Defending champion Francesca Schiavone eased past Vesna Dolonts 6-1 6-2.
Svetlana Kuznetsova, the 2009 champion, brushed past Romania's Irina-Camelia Begu 6-1 6-1 to make the last 32.
Eighth seed Sam Stosur, meanwhile, made short work of Simona Halep with a 6-0 6-2 win.
Given the discrepancy in their rankings, with Wozniacki ranked number one compared to her Canadian opponent's 162, the day's opening match on Court Phillippe Chatrier proved a more even encounter than many expected.
During the deciding tie-break a rattled Wozniacki attracted jeers from the crowd as she disputed a crucial line call for several minutes.
Although the Dane failed to convince the umpire to rule her lob in, Wozniack failed to convert three set points in the aftermath of the delay, and Wozniacki departed the court to more mummurings of disapproval from the specatators.
"I started off really well, and everything was going the way I wanted it to," said Wozniacki.
"Second set, she played better. I started to play a little bit worse."
Wozniacki, , had been first into her stride, taking her Canadian opponent's serve in the second game of the match to gain an immediate advantage.
Wozniak responded with a break of her own in the next game but could neither match Wozniacki's consistency nor find the clean winners to move her out of her comfort zone.
The world number one looked set to serve out the set after only 24 minutes before some belated resistence from Wozniak prolonged the opener.
The 23-year-old converted her fourth break point in the seventh game to claw her way back, before holding her own serve to pose her opponent some questions.
Wozniacki briefly wobbled and offered up a break point that would have brought the set back on serve, before composing herself to close out.
The second proved an altogether tighter affair as Wozniak grew in confidence.
Her scurrying style saved three break points as she began to match Wozniacki blow for blow from the back of the court.
But for all her effort, her nerve failed her as she stood on the brink of forcing a third set.
Wozniacki will play 28th seed Daniela Hantuchova who overcame Italy's Sara Errani 6-1 6-2, while Schiavone faces China's Shuai Peng following the 29th seed's 7-5 6-1 win over Polona Hercoz of Slovenia.
Australian Stosur, last year's beaten finalist, made far swifter progress with an 82-minute victory over Romanian Halep that sets up a meeting with Argentina's Gisela Dulko.
World number 51 Dulko claimed the scalp of Bulgarian 32nd seed Tsvetana Pironkova with a straightforward 6-4 6-2 win.
Tenth seed Jelena Jankovic ousted Vera Dushevina 6-3 6-2 and Russia's 14th seed Anastasia Pavlyuchenkova was a 6-0 7-6 (7-5) victor over Mona Barthel.
Pavlyuchenkova will face Spain's Nuria Llagostera Vives in the next round following the Spaniard's 6-0 6-2 win over France's Alize Cornet.
Meanwhile German 17th seed Julia Goerges recovered from a set down to beat Madrid quarter-finalist Lucie Safarova 2-6 7-5 6-2.
She will have to compete against a partisan crowd and Marion Bartoli in the third round after the French 11th seed finished strongly to take a 6-4 6-7 (1-7) 6-2 win over Belarusian Olga Govortsova.