Holder Ana Ivanovic was made to sweat much more than expected in a 7-6, 6-3 victory over unheralded Italian Sara Errani to reach the second round of the French Open on Sunday.
The eighth-seeded Serb needed two hours and two minutes to break the resilience of world number 44 Errani to set up a meeting with either France's Camille Pin or Tamarine Tamasugarn.
"I expected a tough match. I knew I would have to work hard for my points today, and I'm very happy I did that," Ivanovic told reporters.
"I kept my composure even when I was making a few mistakes."
Ivanovic, who had only won two matches on clay this season before arriving at Roland Garros, threw away 10 break points in the first set and was stretched into a tiebreak which she claimed after 72 minutes.
Errani lost focus in the tiebreak after contesting a call and she paid for it by allowing Ivanovic to move 5-2 up and clinch it 7-3.
Ivanovic staved off four break points in her opening service game of the second set before moving 5-1 up and although Errani pulled a break back, the 21-year-old Serb wrapped up the win on her third match point with a smash.
The former world number one, who did not play last week's Madrid Open because of a knee injury, said she had put the problem behind her despite having her right knee taped.
"I think last year's US Open was a great experience for me, I played when I wasn't fit enough to play and I kept thinking about my injury through the matches," she said.
"It was not going well. Before my matches, before I stepped on court, I was thinking, am I fit enough to play? And I felt fit enough, so I just put it out of my mind, and I don't want to think about it."
Ivanovic added that playing on a sunsoaked Centre Court brought back sweet memories from last year's final, when she beat Russian Dinara Safina for her first grand slam title.
"This morning when I was warming up they were playing highlights on the big screen. It's always good to see, and you always get a little bit excited watching that," she said.
