Coco Gauff lost to unseeded Magda Linette 6-4 6-4 on Monday as she missed out on a place in the Miami Open quarterfinals after a tough day for Americans as holder Danielle Collins, Amanda Anisimova and Ashlyn Krueger also went out in straight sets.
Gauff, seeded third, struggled mightily with her serve, committing 12 double faults and putting just half of her first serves into play while unforced errors piled up against her 34th-ranked Polish opponent.
Linette held her nerve as the South Florida crowd came alive after Gauff pulled ahead 4-3 in the second set and the Pole ultimately prevailed to notch her first win over a top-three player since 2021.
"It was really important for me to keep pressing Coco's serve to make sure she feels the pressure," Linette said.
Next up for Linette is Italian sixth seed Jasmine Paolini, who beat Japan's Naomi Osaka 3-6 6-4 6-4 earlier on Monday.
SABALENKA CRUSHES IT
Top seed Aryna Sabalenka crushed 23 winners including seven aces to overpower defending champion Collins 6-4 6-4 to reach the quarterfinals where she will meet Zheng Qinwen, who beat Krueger 6-2 7-6(3) in their round of 16 match.
World No 1 Sabalenka will be a heavy favourite against Zheng, who has never beaten the Belarusian in their five previous career meetings.
Jessica Pegula was left to fly the flag for the US women after she won the final six games of her match to see off Ukrainian Marta Kostyuk 6-2 6-3.
Pegula, seeded fourth, will meet Briton Emma Raducanu next after the former US Open champion beat Anisimova 6-1 6-3 in hot and humid conditions.
Raducanu did not drop a point on serve in the first set against the 17th seed and outmanoeuvred her in a rally on match point to seal the win.
It will be the first quarterfinal of a WTA 1000 event for the 22-year-old Raducanu, who has split her two previous career meetings with Pegula.
"I know it's going to be a really difficult match but I think I'm playing pretty good tennis," Raducanu told Tennis Channel.
"I'm really happy with the way things are going and more importantly just enjoying finding the competitive spirit again."
On the men's side, Alex De Minaur overcame a third set service break and a crowd enthusiastically backing his Brazilian opponent to take out teenager Joao Fonseca 5-7 7-5 6-3 in a barnburner under the lights to reach the round of 16.
Fonseca was swinging out of his shoes, at one point literally, as he crushed his booming forehand, whipping up the crowd after securing an early break in the deciding set.
But the speedy Australian showed his toughness in difficult conditions, letting out a roar of his own when Fonseca found the net on match point.
"I told myself it's going to be a battle not only against the player but the crowd," De Minaur told Tennis TV.
"Just put your head down, do your work and try to compete for every single point."
Third seed Taylor Fritz blasted a forehand winner on match point to take out Canadian Denis Shapovalov 7-5 6-3 and bring some cheer for US fans, setting up a date with tournament lucky loser Adam Walton in the round of 16.
Fritz's countrymen were not as fortunate, with Frances Tiafoe losing 7-6(11) 5-7 6-2 to Frenchman Arthur Fils and Reilly Opelka falling 7-6(1) 6-3 to Czech Tomas Machac in their third-round matches.
Fils will face top seed Alexander Zverev in the fourth round after the German beat Jordan Thompson 7-5 6-4.