Romanian Simona Halep, the 2018 French Open champion, and American Danielle Collins are the latest big names to crash out of the women's singles at Roland Garros, with Halep admitting she suffered a panic attack during her shock loss to China's Qinwen Zheng.

The two-time grand slam winner looked in control of her match on Friday, taking the opening set and moving ahead with a break.

However, after Zheng claimed the second set and began to dominate the third, Halep called the trainer and had her pulse and blood pressure taken.

The 30-year-old Romanian was given the all-clear to continue, but never looked comfortable against the 19-year-old, struggling for breath and calling for doctors again before she slumped to a 2-6, 6-2, 6-1 loss.

Halep left the court immediately with medical staff before returning to face media, where she admitted she had a panic attack during the match that she could not control.

"I was playing well at the start. I had a break in the second set, but then something happened. I just lost it," she said.

"I didn't expect [that] because it was just a panic attack.

Halep was cleared by medical staff afterwards and said it did not feel like a prolonged problem.

"After the match was pretty tough, but now I'm good. I'm recovered, and I will learn from this episode," she said.

"It's just a tennis match, so I have to see it a little bit more relaxed. [I] probably put pressure on myself too much, because I really wanted to do well.

"I felt good. I practise, I work hard. But it just didn't happen and, probably, I got a little bit of panic during that thinking, over-thinking.

"I knew that I have just to calm down, because the doctors checked everything. Everything was perfect. Not really a reason, just [in the] mind."

Elsewhere, Australian Open finalist and ninth-seed Danielle Collins was bundled out of the tournament by compatriot Shelby Rogers after a 6-4, 6-3 loss, while number eight seed Karolina Pliskova and number 13 seed Jelena Ostapenko also suffered shock defeats.

So swift has been the exit of the women's top seeds that only three of the top 10 remain: Iga Świątek (1), Paula Badosa (3) and Aryna Sabalenka (7).

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Poland's Świątek — the world number one and in the form of her life — brushed aside Alison Riske of the US, 6-0, 6-2, to take her winning streak to 30 matches.

It's the longest winning run in women's tennis since Serena Williams won 34 in a row in 2013.

Spain's Badosa reached the third round by beating Kaja Juvan, of Slovenia, 7-5, 3-6, 6-2 while Sabalenka needed just 62 minutes to beat Madison Brengle 6-1, 6-3.

Madison Keys justified her number 22 seeding when she advanced to the third round with a 6-4, 7-6 (7-3) win over Frenchwoman Caroline Garcia.

The American, a semi-finalist at Roland Garros in 2018, will next face the number 16 seed, Elena Rybakina, the only woman with more aces than Keys this season.

AAP/ABC