Stuttgart: World No.1 Naomi Osaka has made a winning start to her clay-court season by beating Taiwan's Hsieh Su-wei 6-4, 6-3 to move into the quarter-finals of the Porsche Tennis Grand Prix in Stuttgart.
The two-time grand slam champion, who has yet to win a title on clay, found little resistance on Thursday as she avenged her defeat to Hsieh in Miami last month.
"If there is one positive thing I can say about myself, it's that I learn quickly," Osaka said.
"So, for me it has been fun because I like to apply what I did wrong in the past, and I think that is what I was able to do today."
A break was enough for Osaka to win the first set as she looked somewhat uncomfortable on Stuttgart's quick indoor clay, designed to be similar to next month's French Open courts.
There was nothing wrong with her serve, however, as she fired seven aces during the contest.
After going 2-0 up in the second set, Osaka grew in confidence and broke again to seal her first win on clay this season on her first match point.
Victory also meant she will hold on to her world No.1 ranking after this week.
Osaka will next face Croatia's Donna Vekic, who beat Daria Kasatkina 6-1, 7-5.
World No.5 Angelique Kerber had little trouble in the all-German battle against wildcard Andrea Petkovic, beating the former top-10 player 6-2, 6-4.
She will play sixth seed Kiki Bertens, who fired 20 aces as she battled back from a set down to beat Belinda Bencic 4-6, 6-3, 6-4.
Former world No.1 Victoria Azarenka of Belarus stunned fourth seed and defending champion Karolina Pliskova, needing two hours and 13 minutes to battle from a set down to win 4-6, 6-3, 6-4. She next takes on Estonian Anett Kontaveit.
Meanwhile, Rafael Nadal looks closer to his clay-court best again as he beat David Ferrer 6-3, 6-3 to reach the quarter-finals of the Barcelona Open.
The 11-time Barcelona champion saved four of five break points and broke four times on Thursday in what could have been his last meeting with Ferrer, who is retiring after the Madrid Open next month.
It was a sign of improvement for Nadal, who lost in the semi-finals in Monte Carlo last week and then needed three sets to get past Leonard Mayer in his opening match in Barcelona.
"This match was important for me," Nadal said.
"Yesterday I had a tough match. I took a step forward and was able to play with more energy."