Serena Williams admitted skipping the French Open "crossed my mind every day" after recovering from a horror start to her campaign to beat Vitalia Diatchenko.

Williams arrived in Paris having played just four tournaments this year, withdrawing from all of them except the Australian Open, where she lost from 5-1 up in the deciding set of her quarter-final against Karolina Pliskova.

Latterly Williams has been troubled by a left knee problem, and a picture of her sitting in a wheelchair last week when she took her daughter to Disneyland added to concerns about her fitness.

She looked nervous and rusty as Russian Diatchenko, ranked 83rd, took the opening set amid a slew of errors from her opponent, but a roar of frustration let out by Williams seemed to turn things in the right direction and she lost only one of the last 13 games.

"I just got nervous out there and I stopped moving my feet," said Williams. "And it was like concrete blocks on my feet. I was, like, 'You've got to do something'.

"I was just making so many errors. Every shot I hit, I felt like I was hitting on my frame. I usually don't hit balls on my frame. I was just off, basically. And then instead of correcting it, I just kept getting worse.

"I knew it couldn't get worse, and I knew I could only go up. That's what I told myself. I've just got to keep positive."

Of the roar, Williams added: "I just was so frustrated at that point, because I have been training well. I just let out this roar, and here I am. So maybe that helped."

She also tried tweaking her outfit, pulling on a black top, and putting her hair up in a bun as she sought a change in fortune.

"I just needed to change," she said. "I was, like, 'I've got to try something different'. It's not my forehand, it's my clothes, right?"

Twelve months after making her grand slam return in a catsuit that was eventually banned, Williams wore a striking two-piece outfit and, for her entrance, a cape covered with the words 'queen', 'champion', 'goddess' and 'mum' in French.

She has proved many times in the past that her form going into a grand slam is not a reliable indicator of how she might fare, but it would be her most remarkable triumph yet if she could win a 24th grand slam singles title here.

Williams hesitated whether to even play at Roland Garros, saying: "It crossed my mind every day, but I'm here. And to do the best that I can do."

Fourth seed Kiki Bertens, who is hotly fancied to do well, made a confident start with a 6-3 6-4 victory over Pauline Parmentier but 13th seed Caroline Wozniacki crashed out 0-6 6-3 6-3 to Russian Viktoria Kudermetova.

Wozniacki has been struggling with a left calf injury, and she said: "I think I played really well in the first set. And then I think she got very lucky at the start of the second set and took advantage of the opportunities she got.

"And then I think I just lost a little steam in the end and I made some unforced errors that I normally don't do, so that was very frustrating. I haven't had the best lead-up to this tournament."

Sixth seed Petra Kvitova did not take to the court for her scheduled clash with Sorana Cirstea after being diagnosed with a grade two muscle tear in her left forearm.

The two-time Wimbledon champion is hopeful of being fit for the grass-court season.