The top seed and the defending champion were both eliminated Monday in the third round of the BNP Paribas Open in Indian Wells, Calif.
Brazil's Beatriz Haddad Maia, who only made the draw as a lucky loser from qualifying, stunned No.1-seeded Karolina Pliskova of the Czech Republic 6-3, 7-5.
Estonia's Anett Kontaveit, the 18th seed, posted a 7-6 (5), 6-3 win over 16th-seeded Bianca Andreescu, the Canadian who won the event in the Southern California desert in the spring of 2019. The tournament was canceled in 2020 and postponed six months this year due to the COVID-19 pandemic.
Haddad Maia and Kontaveit will meet in the fourth round to vie for a spot in the quarterfinals.
Haddad Maia, 25, is ranked 115th in the world. She has played well in second- and third-tier tournaments this year but had not won a match in a WTA Tour-level event in 2021 before arriving in Indian Wells.
She wasn't intimidated against Pliskova, though, converting eight of her 14 break-point opportunities. Pliskova was hurt by 12 double faults while serving just five aces. Haddad Maia had two aces and four double faults.
Kontaveit jumped in front of Andreescu by winning a tiebreaker that saw the serving player lose nine of the 12 points. The match featured nine service breaks, and Kontaveit pulled away by claiming the final four games overall.
"Today, she was the better player," Andreescu said. "We both, I think, didn't play our best, but she was the better player. I did my best. That's all I can ask for."
Kontaveit added, "It was extremely close throughout the match and I was just trying to stay tough. I was ready for a tough match. She's such a good player, such a great competitor, so I knew it wasn't going to be over until it was really over."
Also advancing to the fourth round were 10th-seeded Angelique Kerber of Germany, 12th-seeded Ons Jabeur of Tunisia, Ajla Tomljanovic of Australia and Anna Kalinskaya of Russia.
--Field Level Media