World No 1 Ashleigh Barty wasted no time on Wednesday booking her place in the quarter-finals of the WTA clay-court tournament in Stuttgart.

The top seed needed just 24 minutes to wrap up the first set against Germany’s Laura Siegemund before claiming a 6-0, 7-5 second-round win.

“It was good to play on a new surface, the court was quite quick compared to what I am used to,” said Barty, who hit six aces in an impressive opening display.

After Charleston, this is Barty’s second clay-court tournament to prepare for next month’s French Open, where she won the 2019 title.

Barty revealed that she was innoculated against the Covid-19 virus while in South Carolina. “It was nice to know that we have got that small layer of protection.”

The 24-year-old Australian sat out Roland Garros last year because of the Covid-19 pandemic and Poland’s Iga Swiatek succeeded her as champion.

In Friday’s quarter-finals, Barty plays either Latvia’s Jelena Ostapenko, also a former Roland Garros winner, or former world No 1 Karolina Pliskova of the Czech Republic.

“They are both good strikers (of the ball), so I will watch their match and see how best to play them,” added Barty.

Earlier, Pliskova had to dig deep after losing the second set to German Tamara Korpatsch before sealing a 7-5, 3-6, 6-3 victory in her opener, her first appearance this season on clay.

“I’m super happy that I’m through, but other than that I didn’t see many really good things,” said Pliskova, currently ranked ninth in the world.

“I was struggling a bit in the rallies. I thought there were too many errors from easy balls, but my serve was quite ok. First rounds are always a bit nervous, especially a first match on clay. I’m just going to hope it’s going to be better.”

There were no such problems for three-time Grand Slam winner Angelique Kerber, who breezed into the second round, sweeping aside Georgia’s Ekaterine Gorgodze in a 6-2, 6-2 victory.

“That wasn’t a bad way to start the clay-court season. She wasn’t an easy opponent and I had a solid game,” said Germany’s Kerber.

The 33-year-old, who has dropped to 26 in the world rankings, expects a “tough match” on Thursday against fourth-seeded Ukrainian Elina Svitolina, who has won all of their last six meetings.

The winner will face Petra Kvitova in Friday’s quarter-final after the seventh seed had to battle hard before sealing a 6-3, 3-6, 6-3 win over Maria Sakkari of Greece.

Sakkari struck eight aces in a two-and-a-half hour tussle as Kvitova dug deep following her hard-fought first-round success over Australian Open finalist Jennifer Brady on Tuesday.

In Wednesday’s other second-round match, third-seeded American Sofia Kenin was knocked out 7-5, 6-4 by Anett Kontaveit of Estonia.

In the quarter-finals, Kontaveit plays either fifth seed Aryna Sabalenka of Belarus or German qualifier Anna-Lena Friedsam.

Second round

Ashleigh Barty (AUS x1) bt Laura Siegemund (GER) 6-0, 7-5

Anett Kontaveit (EST) bt Sofia Kenin (USA x3) 7-5, 6-4

Petra Kvitova (CZE x7) bt Maria Sakkari (GRE) 6-3, 3-6, 6-3

First round

Jelena Ostapenko (LAT) bt Stefanie Voegele (SUI) 6-4, 7-5

Karolina Pliskova (CZE x6) bt Tamara Korpatsch (GER) 7-5, 3-6, 6-3

Angelique Kerber (GER) bt Ekaterine Gorgodze (GEO) 6-2, 6-2

Marketa Vondrousova (CZE) bt Marie Bouzkova (CZE) 6-1, 7-6 (8/6)