Her chopstick skills might not be the best but Naomi Osaka says an improvement in her focus is behind a run of success that culminated in winning the US Open.

The 20-year-old, who stunned Serena Williams to win her maiden Grand Slam last month, was devastating against 10th seed Julia Goerges of Germany on Thursday, winning 6-1, 6-2 in 65 minutes to speed into the China Open quarter-finals.

Osaka, the eighth seed in Beijing, similarly thrashed unseeded American Danielle Collins 6-1, 6-0 in the previous round and is showcasing the ruthlessness that saw her beat Williams in a controversial New York final.

The Japanese will face home hope Zhang Shuai in the last eight in the Chinese capital after Zhang pulled off a shock in defeating three-time Grand Slam champion Angelique Kerber.

China Open organisers have had the players competing in a “chopstick challenge” and Zhang and the German Kerber are currently winning.

Told that she was well behind both with her score, Osaka joked: “We’re not talking about that.

“Come on, with Shuai, let’s face it... But the thing is, I hold chopsticks in a weird way anyways.”

Turning more serious, the world number six, said: “On the court I have to think ‘focus’ because it’s not something that’s natural to me.

“It’s something that I’ve been working on throughout this whole year and I think it finally clicked, or at least it’s more consistent.”

Osaka, who appears increasingly at ease with the media, joking and chatting freely, said that she had also brought more consistency to her game.

“Not so many unforced errors (compared to a year ago). I’m not sure how many I hit today, but sometimes last year I think I was hitting a lot.”

Osaka meets unseeded Zhang next after the Chinese world number 45 emerged from a see-saw battle with third seed Kerber.

Zhang, 29, grabbed the first set 6-1, before reigning Wimbledon champion Kerber fought back to win the second 6-2.

Zhang stepped up a gear in the decider, taking the set with a comprehensive 6-0 to thrill the home crowd.

Kerber said that she had been troubled by a problem with her right knee, but refused to blame that for the defeat.

“I was not feeling the best at the beginning of the match, but then I was playing better and better,” said the 30-year-old.

“At the end she played a good third set – she took her chances and played a really solid match.”