OSAKA, Japan - The last three quarterfinal spots were snapped up at the HP Open on Thursday, with the youngest player in the Top 50 - Top 80, even - the first of the three to advance to the last eight.
In a match-up between two of this year's biggest breakthrough stars, No.6 seed Madison Keys broke away from 3-4 first set against Zhang Shuai, reeling off nine games in a row to win in just 51 minutes, 64 60. Keys lost just three points in the second set and won 20 of the last 21 points of the match.
"I started off a little bit slow, especially returning - I was making a lot of mistakes," Keys said. "But I felt like once I really got going and got a good feeling on the court, I played really well.
"My serve got me out of some tough positions in the first set and really helped in the second set."
Having never been to a WTA quarterfinal previously, Keys is now through to her fourth this year, having already gone this far at Sydney, Charleston and Birmingham - hard, clay and grass, now hard again.
"This has been my first trip to Asia," Keys said. "The people are great and I've really enjoyed being in Japan. I don't mind the heat and I like the surface - it's really fast - so it works for my game."
The only player in the Top 100 younger than the No.39-ranked Keys is the No.81-ranked Donna Vekic.
The last match of the day saw Zheng Jie go right to work after dropping a marathon 69-minute first set, beating No.9 seed Kristina Mladenovic, 67(5) 62 60. Zheng won the last eight games of the match.
"The first set was really close - I think in the most important points I didn't play so well," Zheng said. "She was serving so big. I had never played against her in singles before and she was so tough.
"Early in the second set I started to play more aggressively against her, and I broke her early in both sets, and that helped me because she started thinking about it more. It was very good to break early."
The veteran Zheng pointed to another factor in her win over Mladenovic, an up-and-comer on the tour.
"I think my experience really helped me today," Zheng said. "I've played a lot in my career and she's young. Even though I lost the first set, I stayed really focused and knew that I could win the match."
Next up for Zheng is an even younger prospect - Keys. The two are tied 1-1 in their head-to-head.
"I played her last year and this year, and she's had a big change this year," Zheng said. "Before she just had a good serve and good forehand, but now her backhand is aggressive too. It will be a tough match. I need to focus on my return and get a lot of serves in - I have to serve smart tomorrow."
All four of the quarterfinals will take place at the International-level event on Friday.