Naomi Osaka said Thursday that she was "angry relaxed" after the Japanese tennis player set up a potential first meeting with US Open champion Bianca Andreescu in Beijing.
The 21-year-old, the reigning Australian Open champion, won the last 10 games against unseeded American Alison Riske to surge into the last eight at the China Open, 6-4, 6-0.
Osaka and Andreescu, two young stars of women's tennis, will meet if the 19-year-old Canadian wins her match later Thursday against American qualifier Jennifer Brady.
Osaka has not dropped a set in three matches in the Chinese capital and also did not lose a set on the way to winning her home Pan Pacific Open last month.
It is in contrast to the stuttering form the world number four endured after winning the Australian Open at the start of the year.
"I'm relaxed, but I'm a little bit angry, it's an angry relaxed," said Osaka, asked what was behind her recent success in Japan and now China.
"I know after Australia I was like, 'I'm going to have fun'. It was not fun, I did not have fun."
The Japanese said she took a week off after her last 16 defeat at the US Open, where teenager Andreescu went on to triumph over Serena Williams in the final.
"I was sorting out my thoughts," said Osaka, adding that she has "self-diagnosed ADHD" because "if I tell myself to relax, I play three-set matches.
"Out here, if you see, I'm kind of 'angry' right now, I can get through straight-set wins."