Two of the top three seeds fell Thursday in third-round matches at the National Bank Open in Toronto, with unseeded Beatriz Haddad Maia knocking off No. 1 seed Iga Swiatek and No. 14 Karolina Pliskova taking out third-seeded Maria Sakkari.
Haddad Maia, of Brazil, delivered an inspired effort to hang on to defeat the Switzerland's Swiatek 6–4, 3–6, 7–5, under windy conditions at Sobeys Stadium.
"She just used the conditions better than me," Swiatek said after the loss. "When she was playing with the wind, she was playing really strong balls."
Ranked 24th in the world, Haddad Maia's win is the first in her career over a world No. 1.
"I'm happy and proud of myself and my team," Haddad Maia said. "It's a special moment. It's not always easy to beat the number one on a huge stage and against all the crowd."
The Czech Republic's Pliskova, a finalist in Toronto in 2019, took out Greece's Sakkari 6–1, 6–7 (9), 6–3 to reach the quarterfinals.
Also on Thursday, 10th-seeded American Coco Gauff survived 15 double faults to outlast No. 6 Aryna Sabalenka of Belarus 7–5, 4–6, 7–6 (4) in a match that took three hours, 10 minutes.
Gauff will next face No. 15 Simona Halep of Romania, the 2016 and 2018 tournament winner, who beat Switzerland's Jil Teichmann 6–2, 7–5.
The top six seeds in the tournament have been ousted from the tournament.
In other matches Thursday, No. 7 Jessica Pegula of the United States topped unseeded Camila Giorgi of Italy 3–6, 6–0, 7–5, while fellow American Alison Riske had different luck, losing to Yulia Putintseva of Kazakhstan 6–3, 7–5.
Despite the crowds backing her, hometown favorite Bianca Andreescu of nearby Mississauga, Ontario, couldn't quite make it past China's Qinwen Zheng, losing 7–5, 5–7, 6–2.