Karolina Muchova slides past Naomi Osaka in Beijing

Seventh-seeded Karolina Muchova outlasted 12th-seeded Naomi Osaka in their fourth-round match at the China Open on Tuesday in Beijing.

Muchova bounced back from a break down in both the first and third sets to post a 7-5, 1-6, 7-6 (7) victory. The Czech recorded four aces and 52 winners to offset 50 unforced errors and dispatched the Japan native in 2 hours and 52 minutes.

Muchova was unable to convert triple-match point at 5-4 in the third set, as well as three other match points in the ensuing tiebreaker before winning the ninth on a backhand volley.

"I honestly didn't even believe I will finish the match," Muchova said in her on-court interview. "So many match points, I didn't know how many. After a match point I was like, 'OK, I'm going for it,' but then I think she always played great and steady, and didn't make mistakes – unlike me, unfortunately! I was shaking. I'm happy that I made the last volley and it was really so close. Naomi could be standing here. It's me, and I'm really grateful for it."

Osaka struck 11 aces and converted five of 10 break-point opportunities.

Muchova, 30, advanced to the quarterfinals to set up a maiden matchup against countrywoman Nikola Bartunkova. The 20-year-old Bartunkova followed up her upset of Aryna Sabalenka with a 6-0, 4-6, 6-3 victory over Sinja Kraus of Austria.

"It's been an unbelievable year for me," Bartunkova said after the 1-hour, 46-minute match. "I didn't expect before this year that I play like this and I will be here. It's great, but just now I focus on myself, improve my game because it's still 50-50 every match.

"I'm still young, so I need to have more experience and this is my goal now."

No. 19 seed Ekaterina Alexandrova of Russia breezed to a 6-2, 6-2 victory over Czech Linda Noskova, the tournament's fifth seed.

Noskova committed six double faults on her way to the lopsided loss.

Alexandrova advanced to face fourth-seeded Russian Mirra Andreeva, who coasted to a 6-2, 6-2 win over Ukraine's Daria Snigur.