Top seed Lindsay Davenport and Venus Williams were made to work hard to reach the French Open third round.
Davenport saw opponent Peng Shuai serve for the match in the second set but forced a tie-break and never looked back, wrapping up a 3-6 7-6 6-0 win.
Williams ground out a 6-3 3-6 6-3 victory over Fabiola Zuluaga but only after the Colombian lost her momentum.
Zuluaga handed Williams a 4-0 lead in the decider before staging a late rally but it was too late to save the match.
Williams took the first set but her patchy form saw her surrender the second to the dominant Zuluaga.
And the American will have to sharpen up her game if she is to reach the quarter-finals for the second year running.
The American 24-year-old made 45 unforced errors and hit nine double-faults on her way to losing serve seven times.
"It was a challenging match," said Williams.
"I think the best part was she's a player with variety. I got to see everything I'll see throughout the rest of the tournament."
Davenport took one hour and 37 minutes to see off 19-year-old Peng's challenge.
After losing the first set, the American fought off match-point in the second and then wrapped up the tie-break 7-4 before roaring to the decider without losing a game - as Peng lost all her confidence.
"It was just one of those kind of tough days, and a day I probably shouldn't have ended up winning," said Davenport.
Kim Clijsters took just 56 minutes to book her place in the third round with a 6-2 6-1 win over Slovakia's Ludmila Cervanova.
The French Open runner-up in 2001 and 2003 has been struggling with strained knee ligaments but showed no signs of difficulty.
"I'm still wearing the tape around my knee to protect myself but I feel good," smiled the Belgian.
Dementieva hopes to go one better in Paris this year
Russian fourth seed Elena Dementieva also advanced to the third round with a 7-6 6-2 victory over the nimble Sandra Mamic.
The Croatian chased down every shot and Dementieva was stretched to a tie-break in the opening set, clinching it 9-7.
The Russian broke Mamic to go 4-2 up in the second and effortlessly served out the match.
Dementieva, who lost to compatriot Anastasia Myskina, in last year's final will now face Japan's Akiko Morigami.
Morigami defeated Croat Karolina Sprem, seeded 31, 7-5 6-3.
But there was no such luck for compatriot and 19th seed Shinobu Asagoe, who was upset by Bulgaria's Sesil Karatantcheva 7-5 6-2.
Meanwhile, Emilie Loit gave French fans something to cheer about as she beat 27th seed American Amy Frazier 6-4 6-4.
And 30-year-old Mary Pierce also delighted home fans, thrashing Croatia's Jelena Kostanic 6-1 6-0.