Fresh off a championship run on hardcourt at the Miami Open, the world No.1 cruised past Japan's Misaki Doi 6-2 6-1.

The Queenslander won 10 of the last 11 games in her first match on the slower surface since winning the 2019 French Open.

"There was an adjustment period, without a doubt," Barty said of her second-round match following an opening bye.

"It was a very quick turnaround from Miami, just had a couple of hours of practice. I was, honestly, just hoping I didn't trip and fall over trying to slide.

"But it came back quite naturally. So really happy to be back here, particularly in Charleston, but back on clay."

She'll now play the winner of American Shelby Rogers who beat countrywoman Amanda Anisamova 1-6 7-5 6-4.

Barty was joined in the third round by fellow Australian Ajla Tomljanovic who worked hard in a 4-6 7-5 7-5 win over Czech Marie Bouzkova.

Sloane Stephens awaits for Tomljavonic after she beat American compatriot Madison Keys 6-4 6-4.

Not all the high seeds made the transition as smoothly as Barty.

Second-seeded American Sofia Kenin fell to Lauren Davis of the United States in three sets, 4-6 6-3 6-4.

Kenin, ranked fourth in the world and a former Australian Open champion, was tied in the final set before several errors cost her the match. Kenin put two shots long in the final game to send Davis into the next round.

Davis said she was struggling with her serve early on before slowing down and thinking through her game.

"I found she wasn't too much a fan of high balls," Davis said. "So I really took advantage of that. Really happy with how I composed myself and handled the situation."

Fifth-seeded Belinda Bencic of Switzerland lost in three sets to Spain's Paula Badosa, 6-2 6-7 (7-2) 6-1. And No. 7 Elise Mertens of Belgium fell to Frenchwoman Alize Cornet 7-5 6-3.

Among the seeded players moving on was 17-year-old American Coco Gauff, who topped Russia's Liudmila Samsonova 4-6 6-1 6-4.

Australian Associated Press