Ninth seed Zheng Qinwen finished off Ashlyn Krueger, 6-2, 7-6 (3), to book a last-eight clash with Aryna Sabalenka. The world No. 1 improved to 7-0 against Danielle Collins, advancing past the reigning champion, 6-4, 6-4. Collins will depart the Top 20 next Monday as a result.
Meanwhile, Tiafoe went down in a spirited first-time meeting between competitors separated by one ranking place. World No. 18 Arthur Fils battled to a 7-6 (11), 5-7, 6-2 victory on Grandstand, having saved six set points in the opener and later seeing the 17th-ranked Tiafoe save two match points on his serve at 4-5 in the second set.
The 20-year-old is bidding to reach the quarterfinals at both Sunshine Double stops and next gets top seed Alexander Zverev, a 6-4, 7-5 winner over Jordan Thompson. Tiafoe fell to 9-6 on the year.
